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The support box is constructed much like a shoe box except that one side is missing. The bottom has a rectangle cut out of end (see where Travis's hand is). This allows the bracket assembly to rotate all the way to a position perpendicular to the ground. Also, on the end of the box opposite Travis, cut out a semicircle to allow the telescope to rotate all the way to a position parallel to the ground. The bracket assembly encases the telescope. It looks like this: It is made up of a rectangular three-sided box with end plates on either end (bottom). The end plates (at the top) have wing screws which allow the top half of the end plate to be removed from the tube bracket assembly, releasing the telescope. This is useful for making adjustments to the telescope itself or for using a different powered telescope in the same mounting. Notice also the round wooden pieces attached to either side of the support box in the above picture. Wood glue is applied around the circumference of the circle and the smaller plastic tubes, only about an inch in length, are squeezed on. These are the trunnions. The unique part of the mounting is the trunnion. Trunnion notch plates are attached to the insides of the left and right walls (when looking through the telescope) of the support box. Plastic Furniture tacks are stuck into the insides of the triangular cut-out and support the trunnions. These tacks can be moved at any time to increase or decrease friction so that the trunnions will move smoothly, but also not allow the tube bracket assembly (and thus the telescope) to slip. The tube bracket assembly, telescope, and support box combined can be removed from the base. The result is that our telescope moves freely through an entire hemisphere giving us the ability to look at anything in the sky. It was with this mounting that we were finally able to recreate some of Galileo's observations. If you would like more information on how to build a relatively cheap mounting for your Galilean telescope, just e-mail Tom Williams or Jessica Williams. Return to the astronomy group's home page .

In holography, diffraction gratings are used to produce holograms, which are three-dimensional images of objects. They work by diffracting light from a laser, creating a set of interference patterns that are captured by a photographic plate. The hologram can then be reconstructed as a three-dimensional image by illuminating it with light from the same laser.

The unique part of the mounting is the trunnion. Trunnion notch plates are attached to the insides of the left and right walls (when looking through the telescope) of the support box. Plastic Furniture tacks are stuck into the insides of the triangular cut-out and support the trunnions. These tacks can be moved at any time to increase or decrease friction so that the trunnions will move smoothly, but also not allow the tube bracket assembly (and thus the telescope) to slip. The tube bracket assembly, telescope, and support box combined can be removed from the base. The result is that our telescope moves freely through an entire hemisphere giving us the ability to look at anything in the sky. It was with this mounting that we were finally able to recreate some of Galileo's observations. If you would like more information on how to build a relatively cheap mounting for your Galilean telescope, just e-mail Tom Williams or Jessica Williams. Return to the astronomy group's home page .

As always, Firebird Optics provides a large range of stock and custom diffraction gratings and if you need something custom made please don’t hesitate to e-mail us at info@firebirdoptics.com.

Diffractiongrating pattern

There are three main types of diffraction gratings: transmission gratings, reflection gratings and holographic gratings. Transmission gratings are used to produce spectrums by transmitting light through the grating, while reflection gratings are used to produce laser beams by reflecting light off the grating.

This telescope mounting is composed of a base a support box for the telescope tubing and its bracket assembly a bracket assembly encasing the telescope tubing with trunnion bearings which fit into the trunnion notch plates attached to the inside of the support box Parts List: Polybutylene Pipe Diameter = 4", Length = approximately 5' These can vary. The length is approximately equal to the height that you desire. Polybutylene pipe for the trunnion (swivel) for the telescope tubing Diameter = 2", Length = approximately 2 pieces about 1" long This is glued to the tube bracket assembly with Wood glue Plastic furniture tacks These are used to stick into the bottom of the legs of chairs to protect the floor. They provide the foundation for the trunnions to turn. Wing Screws These are used for the end plates of the tube bracket assembly. They allow for the different telescopes to be used, just by unscrewing these and inserting a different telescope. Plastic floor flanges which can hold the big tubing and be nailed to the wood Nails, Bolts, Screws A whole lot of plywood! Suggested Tools: Power Saw circular saw Power Drill glue work bench to cut out various shapes of wood Instructions: The base is constructed by attaching the plastic holder to a square piece of plywood and then adding four legs which extend outward. The big plastic tubing can be glued into the holder. At the top of the tubing, another plastic holder is put on, but not glued, so that the entire top of the mounting can be removed for adjustments and travel purposes. The top plastic holder is attached to a round piece of plywood which has a whole cut out of the middle and a screw inserted there. The support box will be attached here and can swivel 360 degrees. The support box is constructed much like a shoe box except that one side is missing. The bottom has a rectangle cut out of end (see where Travis's hand is). This allows the bracket assembly to rotate all the way to a position perpendicular to the ground. Also, on the end of the box opposite Travis, cut out a semicircle to allow the telescope to rotate all the way to a position parallel to the ground. The bracket assembly encases the telescope. It looks like this: It is made up of a rectangular three-sided box with end plates on either end (bottom). The end plates (at the top) have wing screws which allow the top half of the end plate to be removed from the tube bracket assembly, releasing the telescope. This is useful for making adjustments to the telescope itself or for using a different powered telescope in the same mounting. Notice also the round wooden pieces attached to either side of the support box in the above picture. Wood glue is applied around the circumference of the circle and the smaller plastic tubes, only about an inch in length, are squeezed on. These are the trunnions. The unique part of the mounting is the trunnion. Trunnion notch plates are attached to the insides of the left and right walls (when looking through the telescope) of the support box. Plastic Furniture tacks are stuck into the insides of the triangular cut-out and support the trunnions. These tacks can be moved at any time to increase or decrease friction so that the trunnions will move smoothly, but also not allow the tube bracket assembly (and thus the telescope) to slip. The tube bracket assembly, telescope, and support box combined can be removed from the base. The result is that our telescope moves freely through an entire hemisphere giving us the ability to look at anything in the sky. It was with this mounting that we were finally able to recreate some of Galileo's observations. If you would like more information on how to build a relatively cheap mounting for your Galilean telescope, just e-mail Tom Williams or Jessica Williams. Return to the astronomy group's home page .

High Resolution: Diffraction gratings can produce high-resolution spectra due to their ability to separate light into its component wavelengths with a high degree of accuracy and precision. This is achieved by making the spacing between the grooves in the grating very small.

From the above picture, you can see that an image, HI, will be viewed upright, making the Galilean telescope useful for terrestrial purposes as well as astronomical. Keplerian telescopes, in contrast, invert the image. What are the disadvantages of a Galilean telescope? The Galilean telescope's biggest disadvantage is its small field of view. A Galilean telescope typically has a field of view of about 15-18 arc minutes. The moon has a diameter of about 30 arc minutes, so the Galilean telescope only reveals approximately one-fourth of the moon's surface at one time. In the Houston skies, a typical field of view has only one star or no stars at all. This makes it very difficult to map a constellation. Increasing the magnification on the Galilean telescope, like all telescopes, reduces the field of view. Perhaps Galileo built a 30X telescope, but it is doubtful that he used much in his observations. The field of view must have been very tiny. How do you make a Galilean telescope?Building the Telescope Tube: Last Year's Group's Work Parts List (With approximate cost): Cardboard Telescoping Mailing Tube (1), $3 Diameter = 50mm (or 2"), Length = 1100mm (or 143") Should be comprised of an inner and outer tube with closed ends on the outer tube. Concave Convex Lens (the "objective lens") (1), $16 for this and the next lens as a pair. Focal Length = 1350mm (0.75 diopter) Cut to our specification of 49mm diameter. Plano Concave Lens (the "eyepiece") (1) Focal Length = -152mm (-6.6 diopter), Diameter = 49mm Cut to our specification of 49mm diameter. Suggested Tools: Coping Saw Alternatively, any other instrument that will make a relatively clean cut through the mailing tube. Drill (bit sizes discussed below) Super Glue Alternatively, any other kind of glue that will firmly hold the inner and outer mailing tubes together. It must be of a thin consistency. Greenlee Punch (optional) Instructions: The basic premise of the telescope tube is to align two lenses the appropriate distance from each other. For this telescope, the lenses are a concave convex (one side curved out and the other curved in) and a plano concave (one flat side and one side curved in). The plano concave lens is used as the "eyepiece" with the plano (flat) side facing the eye. The concave convex is used as the "objective lens" that is aligned with the eyepiece and with the convex side facing the sky. Notice that this lens is actually different than the plano convex lens used in the original Galilean telescope, but still gives the same results. The following design uses pieces of the inner tube of the mailing tube to hold the lenses in place inside the outer tube. This is best illustrated in the following diagram, which shows the cross section of the telescope tube: The outer tube of the mailing tube should have a short end that pulls off, and this can be used for the split in the outer tube shown above. This end will be used to hold the eyepiece. The inner tube must have two pieces (about 1" to 1.5" each) cut off of it that will be used as spacers to hold the objective lens in place. Make these cuts as straight and clean as possible, which will be difficult since the tube is made out of cardboard. A coping saw works pretty well for this. Take the short piece of the outer tube and cut or drill a hole (from 3/16" to 5/16" should be fine) directly in the center of the metal cap on the end. This will be the eyehole. It is important that this hole be as clean as possible (no metal protrusions) so that the the flat side of the eyepiece will fit snugly against the metal cap. An electrician's hole punch or Greenlee Punch works well for this task. If a drill is used, drill with a light pressure, then smooth out the inside surface as much as possible. Place the eyepiece flush (flat side) against the inside of this eyehole. The large piece of the inner mailing tube left will be used to hold this in place. To do this, drill small holes around the outside of the eyepiece tube. Then, with the eyepiece properly in place, slide the inner tube into it, put glue into the holes, and turn the tube a little bit to spread the glue inside. Hold the tube snugly against the lens inside the cap until the glue dries. Now, put this aside and take the large outer tube and the two spacers cut from the inner tube. Cut the closed end off of the outer tube, then use the other end to mount the objective lens (since that end already has a clean cut). Again, the "drill holes - put in glue" technique will be used to hold the spacers in place. First, check how far the inner spacer needs to be placed inside the tube so that the lens and other spacer will be able to sit inside the tube comfortably. Then drill holes in the outer tube around this area and glue in the spacer as before. After the first spacer is in place and dry, place the concave side of the objective lens flush against it, and put the other spacer snugly against the lens to hold it in place (again using the drill - glue method). Now there are two pieces, each containing one of the lenses. Slide the mailing tubes together as shown in the drawing above, and the telescope is done. By leaving these two pieces unglued, the telescope may be focused simply by sliding the eyepiece part inside the objective part. After a desired magnification/focus is found, the two pieces may be permanently attached (or some tape will give a semi-permanent attachment). Two images of a finished tube are shown below. The first picture shows the telescope tube from the objective side while the second image shows the ocular end of the tube: Making the Mounting: This Year's Work For the first half of the semester, we used the mountings built by last year's group. It looked like this: This image was produced by the star jumping in the field of view. We tried to have one person hold the telescope tube steady, but it takes very little movement to cause a star to move across the field of view when the field of view is only about 15 arc minutes. Moreover, our telescope would blow over often and required one person to hold it as still as possible, but this never really worked very well. So, we built a new mounting and stars looked like this, with very little distortion. The new mounting was constructed on a Saturday morning and afternoon, based on plans by Tom Williams. It looks like this: This telescope mounting is composed of a base a support box for the telescope tubing and its bracket assembly a bracket assembly encasing the telescope tubing with trunnion bearings which fit into the trunnion notch plates attached to the inside of the support box Parts List: Polybutylene Pipe Diameter = 4", Length = approximately 5' These can vary. The length is approximately equal to the height that you desire. Polybutylene pipe for the trunnion (swivel) for the telescope tubing Diameter = 2", Length = approximately 2 pieces about 1" long This is glued to the tube bracket assembly with Wood glue Plastic furniture tacks These are used to stick into the bottom of the legs of chairs to protect the floor. They provide the foundation for the trunnions to turn. Wing Screws These are used for the end plates of the tube bracket assembly. They allow for the different telescopes to be used, just by unscrewing these and inserting a different telescope. Plastic floor flanges which can hold the big tubing and be nailed to the wood Nails, Bolts, Screws A whole lot of plywood! Suggested Tools: Power Saw circular saw Power Drill glue work bench to cut out various shapes of wood Instructions: The base is constructed by attaching the plastic holder to a square piece of plywood and then adding four legs which extend outward. The big plastic tubing can be glued into the holder. At the top of the tubing, another plastic holder is put on, but not glued, so that the entire top of the mounting can be removed for adjustments and travel purposes. The top plastic holder is attached to a round piece of plywood which has a whole cut out of the middle and a screw inserted there. The support box will be attached here and can swivel 360 degrees. The support box is constructed much like a shoe box except that one side is missing. The bottom has a rectangle cut out of end (see where Travis's hand is). This allows the bracket assembly to rotate all the way to a position perpendicular to the ground. Also, on the end of the box opposite Travis, cut out a semicircle to allow the telescope to rotate all the way to a position parallel to the ground. The bracket assembly encases the telescope. It looks like this: It is made up of a rectangular three-sided box with end plates on either end (bottom). The end plates (at the top) have wing screws which allow the top half of the end plate to be removed from the tube bracket assembly, releasing the telescope. This is useful for making adjustments to the telescope itself or for using a different powered telescope in the same mounting. Notice also the round wooden pieces attached to either side of the support box in the above picture. Wood glue is applied around the circumference of the circle and the smaller plastic tubes, only about an inch in length, are squeezed on. These are the trunnions. The unique part of the mounting is the trunnion. Trunnion notch plates are attached to the insides of the left and right walls (when looking through the telescope) of the support box. Plastic Furniture tacks are stuck into the insides of the triangular cut-out and support the trunnions. These tacks can be moved at any time to increase or decrease friction so that the trunnions will move smoothly, but also not allow the tube bracket assembly (and thus the telescope) to slip. The tube bracket assembly, telescope, and support box combined can be removed from the base. The result is that our telescope moves freely through an entire hemisphere giving us the ability to look at anything in the sky. It was with this mounting that we were finally able to recreate some of Galileo's observations. If you would like more information on how to build a relatively cheap mounting for your Galilean telescope, just e-mail Tom Williams or Jessica Williams. Return to the astronomy group's home page .

In conclusion, diffraction gratings are an important tool in spectroscopy and have a wide range of applications in other areas, such as holography and laser technology. Despite some limitations, their advantages, including high-resolution spectra and versatility, make them a valuable solution for many applications.

This image was produced by the star jumping in the field of view. We tried to have one person hold the telescope tube steady, but it takes very little movement to cause a star to move across the field of view when the field of view is only about 15 arc minutes. Moreover, our telescope would blow over often and required one person to hold it as still as possible, but this never really worked very well. So, we built a new mounting and stars looked like this, with very little distortion. The new mounting was constructed on a Saturday morning and afternoon, based on plans by Tom Williams. It looks like this: This telescope mounting is composed of a base a support box for the telescope tubing and its bracket assembly a bracket assembly encasing the telescope tubing with trunnion bearings which fit into the trunnion notch plates attached to the inside of the support box Parts List: Polybutylene Pipe Diameter = 4", Length = approximately 5' These can vary. The length is approximately equal to the height that you desire. Polybutylene pipe for the trunnion (swivel) for the telescope tubing Diameter = 2", Length = approximately 2 pieces about 1" long This is glued to the tube bracket assembly with Wood glue Plastic furniture tacks These are used to stick into the bottom of the legs of chairs to protect the floor. They provide the foundation for the trunnions to turn. Wing Screws These are used for the end plates of the tube bracket assembly. They allow for the different telescopes to be used, just by unscrewing these and inserting a different telescope. Plastic floor flanges which can hold the big tubing and be nailed to the wood Nails, Bolts, Screws A whole lot of plywood! Suggested Tools: Power Saw circular saw Power Drill glue work bench to cut out various shapes of wood Instructions: The base is constructed by attaching the plastic holder to a square piece of plywood and then adding four legs which extend outward. The big plastic tubing can be glued into the holder. At the top of the tubing, another plastic holder is put on, but not glued, so that the entire top of the mounting can be removed for adjustments and travel purposes. The top plastic holder is attached to a round piece of plywood which has a whole cut out of the middle and a screw inserted there. The support box will be attached here and can swivel 360 degrees. The support box is constructed much like a shoe box except that one side is missing. The bottom has a rectangle cut out of end (see where Travis's hand is). This allows the bracket assembly to rotate all the way to a position perpendicular to the ground. Also, on the end of the box opposite Travis, cut out a semicircle to allow the telescope to rotate all the way to a position parallel to the ground. The bracket assembly encases the telescope. It looks like this: It is made up of a rectangular three-sided box with end plates on either end (bottom). The end plates (at the top) have wing screws which allow the top half of the end plate to be removed from the tube bracket assembly, releasing the telescope. This is useful for making adjustments to the telescope itself or for using a different powered telescope in the same mounting. Notice also the round wooden pieces attached to either side of the support box in the above picture. Wood glue is applied around the circumference of the circle and the smaller plastic tubes, only about an inch in length, are squeezed on. These are the trunnions. The unique part of the mounting is the trunnion. Trunnion notch plates are attached to the insides of the left and right walls (when looking through the telescope) of the support box. Plastic Furniture tacks are stuck into the insides of the triangular cut-out and support the trunnions. These tacks can be moved at any time to increase or decrease friction so that the trunnions will move smoothly, but also not allow the tube bracket assembly (and thus the telescope) to slip. The tube bracket assembly, telescope, and support box combined can be removed from the base. The result is that our telescope moves freely through an entire hemisphere giving us the ability to look at anything in the sky. It was with this mounting that we were finally able to recreate some of Galileo's observations. If you would like more information on how to build a relatively cheap mounting for your Galilean telescope, just e-mail Tom Williams or Jessica Williams. Return to the astronomy group's home page .

Diffraction gratings are used in a variety of applications, including spectroscopy, holography, and laser technology. In spectroscopy, diffraction gratings are utilized to analyze the composition of materials. They are used to split light into its component wavelengths and measure the intensity of each wavelength. This information can then be used to identify the elements present in a sample and to determine their proportions.

Spectral Distortion: Diffraction gratings can produce spectral distortion, which can result in inaccuracies in the spectra produced. This can be caused by factors such as uneven spacing between the grooves, or non-uniformity in the grooves themselves.

Planediffractiongrating

Wide Wavelength Range: Diffraction gratings are capable of operating over a wide range of wavelengths, making them suitable for use in a variety of applications, including spectroscopy, holography, and laser technology.

The new mounting was constructed on a Saturday morning and afternoon, based on plans by Tom Williams. It looks like this: This telescope mounting is composed of a base a support box for the telescope tubing and its bracket assembly a bracket assembly encasing the telescope tubing with trunnion bearings which fit into the trunnion notch plates attached to the inside of the support box Parts List: Polybutylene Pipe Diameter = 4", Length = approximately 5' These can vary. The length is approximately equal to the height that you desire. Polybutylene pipe for the trunnion (swivel) for the telescope tubing Diameter = 2", Length = approximately 2 pieces about 1" long This is glued to the tube bracket assembly with Wood glue Plastic furniture tacks These are used to stick into the bottom of the legs of chairs to protect the floor. They provide the foundation for the trunnions to turn. Wing Screws These are used for the end plates of the tube bracket assembly. They allow for the different telescopes to be used, just by unscrewing these and inserting a different telescope. Plastic floor flanges which can hold the big tubing and be nailed to the wood Nails, Bolts, Screws A whole lot of plywood! Suggested Tools: Power Saw circular saw Power Drill glue work bench to cut out various shapes of wood Instructions: The base is constructed by attaching the plastic holder to a square piece of plywood and then adding four legs which extend outward. The big plastic tubing can be glued into the holder. At the top of the tubing, another plastic holder is put on, but not glued, so that the entire top of the mounting can be removed for adjustments and travel purposes. The top plastic holder is attached to a round piece of plywood which has a whole cut out of the middle and a screw inserted there. The support box will be attached here and can swivel 360 degrees. The support box is constructed much like a shoe box except that one side is missing. The bottom has a rectangle cut out of end (see where Travis's hand is). This allows the bracket assembly to rotate all the way to a position perpendicular to the ground. Also, on the end of the box opposite Travis, cut out a semicircle to allow the telescope to rotate all the way to a position parallel to the ground. The bracket assembly encases the telescope. It looks like this: It is made up of a rectangular three-sided box with end plates on either end (bottom). The end plates (at the top) have wing screws which allow the top half of the end plate to be removed from the tube bracket assembly, releasing the telescope. This is useful for making adjustments to the telescope itself or for using a different powered telescope in the same mounting. Notice also the round wooden pieces attached to either side of the support box in the above picture. Wood glue is applied around the circumference of the circle and the smaller plastic tubes, only about an inch in length, are squeezed on. These are the trunnions. The unique part of the mounting is the trunnion. Trunnion notch plates are attached to the insides of the left and right walls (when looking through the telescope) of the support box. Plastic Furniture tacks are stuck into the insides of the triangular cut-out and support the trunnions. These tacks can be moved at any time to increase or decrease friction so that the trunnions will move smoothly, but also not allow the tube bracket assembly (and thus the telescope) to slip. The tube bracket assembly, telescope, and support box combined can be removed from the base. The result is that our telescope moves freely through an entire hemisphere giving us the ability to look at anything in the sky. It was with this mounting that we were finally able to recreate some of Galileo's observations. If you would like more information on how to build a relatively cheap mounting for your Galilean telescope, just e-mail Tom Williams or Jessica Williams. Return to the astronomy group's home page .

Now, put this aside and take the large outer tube and the two spacers cut from the inner tube. Cut the closed end off of the outer tube, then use the other end to mount the objective lens (since that end already has a clean cut). Again, the "drill holes - put in glue" technique will be used to hold the spacers in place. First, check how far the inner spacer needs to be placed inside the tube so that the lens and other spacer will be able to sit inside the tube comfortably. Then drill holes in the outer tube around this area and glue in the spacer as before. After the first spacer is in place and dry, place the concave side of the objective lens flush against it, and put the other spacer snugly against the lens to hold it in place (again using the drill - glue method). Now there are two pieces, each containing one of the lenses. Slide the mailing tubes together as shown in the drawing above, and the telescope is done. By leaving these two pieces unglued, the telescope may be focused simply by sliding the eyepiece part inside the objective part. After a desired magnification/focus is found, the two pieces may be permanently attached (or some tape will give a semi-permanent attachment). Two images of a finished tube are shown below. The first picture shows the telescope tube from the objective side while the second image shows the ocular end of the tube: Making the Mounting: This Year's Work For the first half of the semester, we used the mountings built by last year's group. It looked like this: This image was produced by the star jumping in the field of view. We tried to have one person hold the telescope tube steady, but it takes very little movement to cause a star to move across the field of view when the field of view is only about 15 arc minutes. Moreover, our telescope would blow over often and required one person to hold it as still as possible, but this never really worked very well. So, we built a new mounting and stars looked like this, with very little distortion. The new mounting was constructed on a Saturday morning and afternoon, based on plans by Tom Williams. It looks like this: This telescope mounting is composed of a base a support box for the telescope tubing and its bracket assembly a bracket assembly encasing the telescope tubing with trunnion bearings which fit into the trunnion notch plates attached to the inside of the support box Parts List: Polybutylene Pipe Diameter = 4", Length = approximately 5' These can vary. The length is approximately equal to the height that you desire. Polybutylene pipe for the trunnion (swivel) for the telescope tubing Diameter = 2", Length = approximately 2 pieces about 1" long This is glued to the tube bracket assembly with Wood glue Plastic furniture tacks These are used to stick into the bottom of the legs of chairs to protect the floor. They provide the foundation for the trunnions to turn. Wing Screws These are used for the end plates of the tube bracket assembly. They allow for the different telescopes to be used, just by unscrewing these and inserting a different telescope. Plastic floor flanges which can hold the big tubing and be nailed to the wood Nails, Bolts, Screws A whole lot of plywood! Suggested Tools: Power Saw circular saw Power Drill glue work bench to cut out various shapes of wood Instructions: The base is constructed by attaching the plastic holder to a square piece of plywood and then adding four legs which extend outward. The big plastic tubing can be glued into the holder. At the top of the tubing, another plastic holder is put on, but not glued, so that the entire top of the mounting can be removed for adjustments and travel purposes. The top plastic holder is attached to a round piece of plywood which has a whole cut out of the middle and a screw inserted there. The support box will be attached here and can swivel 360 degrees. The support box is constructed much like a shoe box except that one side is missing. The bottom has a rectangle cut out of end (see where Travis's hand is). This allows the bracket assembly to rotate all the way to a position perpendicular to the ground. Also, on the end of the box opposite Travis, cut out a semicircle to allow the telescope to rotate all the way to a position parallel to the ground. The bracket assembly encases the telescope. It looks like this: It is made up of a rectangular three-sided box with end plates on either end (bottom). The end plates (at the top) have wing screws which allow the top half of the end plate to be removed from the tube bracket assembly, releasing the telescope. This is useful for making adjustments to the telescope itself or for using a different powered telescope in the same mounting. Notice also the round wooden pieces attached to either side of the support box in the above picture. Wood glue is applied around the circumference of the circle and the smaller plastic tubes, only about an inch in length, are squeezed on. These are the trunnions. The unique part of the mounting is the trunnion. Trunnion notch plates are attached to the insides of the left and right walls (when looking through the telescope) of the support box. Plastic Furniture tacks are stuck into the insides of the triangular cut-out and support the trunnions. These tacks can be moved at any time to increase or decrease friction so that the trunnions will move smoothly, but also not allow the tube bracket assembly (and thus the telescope) to slip. The tube bracket assembly, telescope, and support box combined can be removed from the base. The result is that our telescope moves freely through an entire hemisphere giving us the ability to look at anything in the sky. It was with this mounting that we were finally able to recreate some of Galileo's observations. If you would like more information on how to build a relatively cheap mounting for your Galilean telescope, just e-mail Tom Williams or Jessica Williams. Return to the astronomy group's home page .

If you would like more information on how to build a relatively cheap mounting for your Galilean telescope, just e-mail Tom Williams or Jessica Williams. Return to the astronomy group's home page .

Holographic diffraction gratings have several advantages over conventional mechanical or embossed gratings. They have a higher diffraction efficiency, which means that more light is diffracted by the grating, and they can have a very high spatial frequency, which allows for a finer grating spacing and improved spectral resolution. They also have the ability to produce gratings with a large surface area and high groove density, which makes them ideal for high-resolution spectroscopy and laser beam steering applications.

It is made up of a rectangular three-sided box with end plates on either end (bottom). The end plates (at the top) have wing screws which allow the top half of the end plate to be removed from the tube bracket assembly, releasing the telescope. This is useful for making adjustments to the telescope itself or for using a different powered telescope in the same mounting. Notice also the round wooden pieces attached to either side of the support box in the above picture. Wood glue is applied around the circumference of the circle and the smaller plastic tubes, only about an inch in length, are squeezed on. These are the trunnions. The unique part of the mounting is the trunnion. Trunnion notch plates are attached to the insides of the left and right walls (when looking through the telescope) of the support box. Plastic Furniture tacks are stuck into the insides of the triangular cut-out and support the trunnions. These tacks can be moved at any time to increase or decrease friction so that the trunnions will move smoothly, but also not allow the tube bracket assembly (and thus the telescope) to slip. The tube bracket assembly, telescope, and support box combined can be removed from the base. The result is that our telescope moves freely through an entire hemisphere giving us the ability to look at anything in the sky. It was with this mounting that we were finally able to recreate some of Galileo's observations. If you would like more information on how to build a relatively cheap mounting for your Galilean telescope, just e-mail Tom Williams or Jessica Williams. Return to the astronomy group's home page .

Diffraction gratings are essential components in various optical systems and applications. The two main types of diffraction gratings, transmission gratings and reflection gratings, have different structures, applications, and advantages, and they are selected based on the specific requirements of the system or application. Whether it is for spectroscopy, optical communications, or laser systems, diffraction gratings play a crucial role in the separation and manipulation of light.

In addition to their high performance, holographic diffraction gratings are also versatile and flexible, as they can be easily produced in a variety of shapes and sizes to meet the specific requirements of an application. They can also be produced in a single step, making them less time-consuming and cost-effective compared to conventional mechanical gratings.

Today, diffraction gratings are widely used in various optical systems and applications, such as spectroscopy, optical communications, laser systems, and imaging. The development of new technologies and materials has allowed for the production of high-performance diffraction gratings with improved efficiency, accuracy, and versatility, making them an essential component in many optical systems and applications.

Cost-effective: Compared to other types of spectroscopy equipment, diffraction gratings are relatively inexpensive, making them a cost-effective solution for many applications.

Diffractiongrating PDF

How does a Galilean telescope work? The Galilean telescope was innovative in that he was the first to expand the range of magnification of the new spyglasses beyond 3X, using his particular set of lenses. In Sidereus Nuncius, Galileo described how these two lenses served to magnify an object. "When there are no glasses in the tube, the rays proceed to the object FG along the straight lines ECF and EDG, but with the glasses put in they proceed along the refracted lines ECH and EDI. They are indeed squeezed together and where before, free, they were directed to the object FG, now they only grasp the part HI" Galileo, Sidereus Nuncius tr. Albert Van Helden, pp. 38-39. Actually, Galileo could not explain how his telescope magnified precisely. He did not understand, as we now know, that the magnification of his telescope can be computed by F/f (see top figure). Increasing the magnification requires lengthening the telescope. Our 10X telescope is about 4 feet long. From the above picture, you can see that an image, HI, will be viewed upright, making the Galilean telescope useful for terrestrial purposes as well as astronomical. Keplerian telescopes, in contrast, invert the image. What are the disadvantages of a Galilean telescope? The Galilean telescope's biggest disadvantage is its small field of view. A Galilean telescope typically has a field of view of about 15-18 arc minutes. The moon has a diameter of about 30 arc minutes, so the Galilean telescope only reveals approximately one-fourth of the moon's surface at one time. In the Houston skies, a typical field of view has only one star or no stars at all. This makes it very difficult to map a constellation. Increasing the magnification on the Galilean telescope, like all telescopes, reduces the field of view. Perhaps Galileo built a 30X telescope, but it is doubtful that he used much in his observations. The field of view must have been very tiny. How do you make a Galilean telescope?Building the Telescope Tube: Last Year's Group's Work Parts List (With approximate cost): Cardboard Telescoping Mailing Tube (1), $3 Diameter = 50mm (or 2"), Length = 1100mm (or 143") Should be comprised of an inner and outer tube with closed ends on the outer tube. Concave Convex Lens (the "objective lens") (1), $16 for this and the next lens as a pair. Focal Length = 1350mm (0.75 diopter) Cut to our specification of 49mm diameter. Plano Concave Lens (the "eyepiece") (1) Focal Length = -152mm (-6.6 diopter), Diameter = 49mm Cut to our specification of 49mm diameter. Suggested Tools: Coping Saw Alternatively, any other instrument that will make a relatively clean cut through the mailing tube. Drill (bit sizes discussed below) Super Glue Alternatively, any other kind of glue that will firmly hold the inner and outer mailing tubes together. It must be of a thin consistency. Greenlee Punch (optional) Instructions: The basic premise of the telescope tube is to align two lenses the appropriate distance from each other. For this telescope, the lenses are a concave convex (one side curved out and the other curved in) and a plano concave (one flat side and one side curved in). The plano concave lens is used as the "eyepiece" with the plano (flat) side facing the eye. The concave convex is used as the "objective lens" that is aligned with the eyepiece and with the convex side facing the sky. Notice that this lens is actually different than the plano convex lens used in the original Galilean telescope, but still gives the same results. The following design uses pieces of the inner tube of the mailing tube to hold the lenses in place inside the outer tube. This is best illustrated in the following diagram, which shows the cross section of the telescope tube: The outer tube of the mailing tube should have a short end that pulls off, and this can be used for the split in the outer tube shown above. This end will be used to hold the eyepiece. The inner tube must have two pieces (about 1" to 1.5" each) cut off of it that will be used as spacers to hold the objective lens in place. Make these cuts as straight and clean as possible, which will be difficult since the tube is made out of cardboard. A coping saw works pretty well for this. Take the short piece of the outer tube and cut or drill a hole (from 3/16" to 5/16" should be fine) directly in the center of the metal cap on the end. This will be the eyehole. It is important that this hole be as clean as possible (no metal protrusions) so that the the flat side of the eyepiece will fit snugly against the metal cap. An electrician's hole punch or Greenlee Punch works well for this task. If a drill is used, drill with a light pressure, then smooth out the inside surface as much as possible. Place the eyepiece flush (flat side) against the inside of this eyehole. The large piece of the inner mailing tube left will be used to hold this in place. To do this, drill small holes around the outside of the eyepiece tube. Then, with the eyepiece properly in place, slide the inner tube into it, put glue into the holes, and turn the tube a little bit to spread the glue inside. Hold the tube snugly against the lens inside the cap until the glue dries. Now, put this aside and take the large outer tube and the two spacers cut from the inner tube. Cut the closed end off of the outer tube, then use the other end to mount the objective lens (since that end already has a clean cut). Again, the "drill holes - put in glue" technique will be used to hold the spacers in place. First, check how far the inner spacer needs to be placed inside the tube so that the lens and other spacer will be able to sit inside the tube comfortably. Then drill holes in the outer tube around this area and glue in the spacer as before. After the first spacer is in place and dry, place the concave side of the objective lens flush against it, and put the other spacer snugly against the lens to hold it in place (again using the drill - glue method). Now there are two pieces, each containing one of the lenses. Slide the mailing tubes together as shown in the drawing above, and the telescope is done. By leaving these two pieces unglued, the telescope may be focused simply by sliding the eyepiece part inside the objective part. After a desired magnification/focus is found, the two pieces may be permanently attached (or some tape will give a semi-permanent attachment). Two images of a finished tube are shown below. The first picture shows the telescope tube from the objective side while the second image shows the ocular end of the tube: Making the Mounting: This Year's Work For the first half of the semester, we used the mountings built by last year's group. It looked like this: This image was produced by the star jumping in the field of view. We tried to have one person hold the telescope tube steady, but it takes very little movement to cause a star to move across the field of view when the field of view is only about 15 arc minutes. Moreover, our telescope would blow over often and required one person to hold it as still as possible, but this never really worked very well. So, we built a new mounting and stars looked like this, with very little distortion. The new mounting was constructed on a Saturday morning and afternoon, based on plans by Tom Williams. It looks like this: This telescope mounting is composed of a base a support box for the telescope tubing and its bracket assembly a bracket assembly encasing the telescope tubing with trunnion bearings which fit into the trunnion notch plates attached to the inside of the support box Parts List: Polybutylene Pipe Diameter = 4", Length = approximately 5' These can vary. The length is approximately equal to the height that you desire. Polybutylene pipe for the trunnion (swivel) for the telescope tubing Diameter = 2", Length = approximately 2 pieces about 1" long This is glued to the tube bracket assembly with Wood glue Plastic furniture tacks These are used to stick into the bottom of the legs of chairs to protect the floor. They provide the foundation for the trunnions to turn. Wing Screws These are used for the end plates of the tube bracket assembly. They allow for the different telescopes to be used, just by unscrewing these and inserting a different telescope. Plastic floor flanges which can hold the big tubing and be nailed to the wood Nails, Bolts, Screws A whole lot of plywood! Suggested Tools: Power Saw circular saw Power Drill glue work bench to cut out various shapes of wood Instructions: The base is constructed by attaching the plastic holder to a square piece of plywood and then adding four legs which extend outward. The big plastic tubing can be glued into the holder. At the top of the tubing, another plastic holder is put on, but not glued, so that the entire top of the mounting can be removed for adjustments and travel purposes. The top plastic holder is attached to a round piece of plywood which has a whole cut out of the middle and a screw inserted there. The support box will be attached here and can swivel 360 degrees. The support box is constructed much like a shoe box except that one side is missing. The bottom has a rectangle cut out of end (see where Travis's hand is). This allows the bracket assembly to rotate all the way to a position perpendicular to the ground. Also, on the end of the box opposite Travis, cut out a semicircle to allow the telescope to rotate all the way to a position parallel to the ground. The bracket assembly encases the telescope. It looks like this: It is made up of a rectangular three-sided box with end plates on either end (bottom). The end plates (at the top) have wing screws which allow the top half of the end plate to be removed from the tube bracket assembly, releasing the telescope. This is useful for making adjustments to the telescope itself or for using a different powered telescope in the same mounting. Notice also the round wooden pieces attached to either side of the support box in the above picture. Wood glue is applied around the circumference of the circle and the smaller plastic tubes, only about an inch in length, are squeezed on. These are the trunnions. The unique part of the mounting is the trunnion. Trunnion notch plates are attached to the insides of the left and right walls (when looking through the telescope) of the support box. Plastic Furniture tacks are stuck into the insides of the triangular cut-out and support the trunnions. These tacks can be moved at any time to increase or decrease friction so that the trunnions will move smoothly, but also not allow the tube bracket assembly (and thus the telescope) to slip. The tube bracket assembly, telescope, and support box combined can be removed from the base. The result is that our telescope moves freely through an entire hemisphere giving us the ability to look at anything in the sky. It was with this mounting that we were finally able to recreate some of Galileo's observations. If you would like more information on how to build a relatively cheap mounting for your Galilean telescope, just e-mail Tom Williams or Jessica Williams. Return to the astronomy group's home page .

Diffractiongrating diagram

The base is constructed by attaching the plastic holder to a square piece of plywood and then adding four legs which extend outward. The big plastic tubing can be glued into the holder. At the top of the tubing, another plastic holder is put on, but not glued, so that the entire top of the mounting can be removed for adjustments and travel purposes. The top plastic holder is attached to a round piece of plywood which has a whole cut out of the middle and a screw inserted there. The support box will be attached here and can swivel 360 degrees. The support box is constructed much like a shoe box except that one side is missing. The bottom has a rectangle cut out of end (see where Travis's hand is). This allows the bracket assembly to rotate all the way to a position perpendicular to the ground. Also, on the end of the box opposite Travis, cut out a semicircle to allow the telescope to rotate all the way to a position parallel to the ground. The bracket assembly encases the telescope. It looks like this: It is made up of a rectangular three-sided box with end plates on either end (bottom). The end plates (at the top) have wing screws which allow the top half of the end plate to be removed from the tube bracket assembly, releasing the telescope. This is useful for making adjustments to the telescope itself or for using a different powered telescope in the same mounting. Notice also the round wooden pieces attached to either side of the support box in the above picture. Wood glue is applied around the circumference of the circle and the smaller plastic tubes, only about an inch in length, are squeezed on. These are the trunnions. The unique part of the mounting is the trunnion. Trunnion notch plates are attached to the insides of the left and right walls (when looking through the telescope) of the support box. Plastic Furniture tacks are stuck into the insides of the triangular cut-out and support the trunnions. These tacks can be moved at any time to increase or decrease friction so that the trunnions will move smoothly, but also not allow the tube bracket assembly (and thus the telescope) to slip. The tube bracket assembly, telescope, and support box combined can be removed from the base. The result is that our telescope moves freely through an entire hemisphere giving us the ability to look at anything in the sky. It was with this mounting that we were finally able to recreate some of Galileo's observations. If you would like more information on how to build a relatively cheap mounting for your Galilean telescope, just e-mail Tom Williams or Jessica Williams. Return to the astronomy group's home page .

Sensitive to Surface Damage: Diffraction gratings are sensitive to surface damage, such as scratches, and this can affect their performance.

In laser technology, diffraction gratings are used to produce laser beams by reflecting laser light off the grating. By adjusting the spacing between the lines or grooves, it is possible to produce a specific wavelength or spectrum of light. This is useful in applications such as laser spectroscopy and in laser cutting and welding.

Making the Mounting: This Year's Work For the first half of the semester, we used the mountings built by last year's group. It looked like this: This image was produced by the star jumping in the field of view. We tried to have one person hold the telescope tube steady, but it takes very little movement to cause a star to move across the field of view when the field of view is only about 15 arc minutes. Moreover, our telescope would blow over often and required one person to hold it as still as possible, but this never really worked very well. So, we built a new mounting and stars looked like this, with very little distortion. The new mounting was constructed on a Saturday morning and afternoon, based on plans by Tom Williams. It looks like this: This telescope mounting is composed of a base a support box for the telescope tubing and its bracket assembly a bracket assembly encasing the telescope tubing with trunnion bearings which fit into the trunnion notch plates attached to the inside of the support box Parts List: Polybutylene Pipe Diameter = 4", Length = approximately 5' These can vary. The length is approximately equal to the height that you desire. Polybutylene pipe for the trunnion (swivel) for the telescope tubing Diameter = 2", Length = approximately 2 pieces about 1" long This is glued to the tube bracket assembly with Wood glue Plastic furniture tacks These are used to stick into the bottom of the legs of chairs to protect the floor. They provide the foundation for the trunnions to turn. Wing Screws These are used for the end plates of the tube bracket assembly. They allow for the different telescopes to be used, just by unscrewing these and inserting a different telescope. Plastic floor flanges which can hold the big tubing and be nailed to the wood Nails, Bolts, Screws A whole lot of plywood! Suggested Tools: Power Saw circular saw Power Drill glue work bench to cut out various shapes of wood Instructions: The base is constructed by attaching the plastic holder to a square piece of plywood and then adding four legs which extend outward. The big plastic tubing can be glued into the holder. At the top of the tubing, another plastic holder is put on, but not glued, so that the entire top of the mounting can be removed for adjustments and travel purposes. The top plastic holder is attached to a round piece of plywood which has a whole cut out of the middle and a screw inserted there. The support box will be attached here and can swivel 360 degrees. The support box is constructed much like a shoe box except that one side is missing. The bottom has a rectangle cut out of end (see where Travis's hand is). This allows the bracket assembly to rotate all the way to a position perpendicular to the ground. Also, on the end of the box opposite Travis, cut out a semicircle to allow the telescope to rotate all the way to a position parallel to the ground. The bracket assembly encases the telescope. It looks like this: It is made up of a rectangular three-sided box with end plates on either end (bottom). The end plates (at the top) have wing screws which allow the top half of the end plate to be removed from the tube bracket assembly, releasing the telescope. This is useful for making adjustments to the telescope itself or for using a different powered telescope in the same mounting. Notice also the round wooden pieces attached to either side of the support box in the above picture. Wood glue is applied around the circumference of the circle and the smaller plastic tubes, only about an inch in length, are squeezed on. These are the trunnions. The unique part of the mounting is the trunnion. Trunnion notch plates are attached to the insides of the left and right walls (when looking through the telescope) of the support box. Plastic Furniture tacks are stuck into the insides of the triangular cut-out and support the trunnions. These tacks can be moved at any time to increase or decrease friction so that the trunnions will move smoothly, but also not allow the tube bracket assembly (and thus the telescope) to slip. The tube bracket assembly, telescope, and support box combined can be removed from the base. The result is that our telescope moves freely through an entire hemisphere giving us the ability to look at anything in the sky. It was with this mounting that we were finally able to recreate some of Galileo's observations. If you would like more information on how to build a relatively cheap mounting for your Galilean telescope, just e-mail Tom Williams or Jessica Williams. Return to the astronomy group's home page .

The result is that our telescope moves freely through an entire hemisphere giving us the ability to look at anything in the sky. It was with this mounting that we were finally able to recreate some of Galileo's observations. If you would like more information on how to build a relatively cheap mounting for your Galilean telescope, just e-mail Tom Williams or Jessica Williams. Return to the astronomy group's home page .

The following design uses pieces of the inner tube of the mailing tube to hold the lenses in place inside the outer tube. This is best illustrated in the following diagram, which shows the cross section of the telescope tube: The outer tube of the mailing tube should have a short end that pulls off, and this can be used for the split in the outer tube shown above. This end will be used to hold the eyepiece. The inner tube must have two pieces (about 1" to 1.5" each) cut off of it that will be used as spacers to hold the objective lens in place. Make these cuts as straight and clean as possible, which will be difficult since the tube is made out of cardboard. A coping saw works pretty well for this. Take the short piece of the outer tube and cut or drill a hole (from 3/16" to 5/16" should be fine) directly in the center of the metal cap on the end. This will be the eyehole. It is important that this hole be as clean as possible (no metal protrusions) so that the the flat side of the eyepiece will fit snugly against the metal cap. An electrician's hole punch or Greenlee Punch works well for this task. If a drill is used, drill with a light pressure, then smooth out the inside surface as much as possible. Place the eyepiece flush (flat side) against the inside of this eyehole. The large piece of the inner mailing tube left will be used to hold this in place. To do this, drill small holes around the outside of the eyepiece tube. Then, with the eyepiece properly in place, slide the inner tube into it, put glue into the holes, and turn the tube a little bit to spread the glue inside. Hold the tube snugly against the lens inside the cap until the glue dries. Now, put this aside and take the large outer tube and the two spacers cut from the inner tube. Cut the closed end off of the outer tube, then use the other end to mount the objective lens (since that end already has a clean cut). Again, the "drill holes - put in glue" technique will be used to hold the spacers in place. First, check how far the inner spacer needs to be placed inside the tube so that the lens and other spacer will be able to sit inside the tube comfortably. Then drill holes in the outer tube around this area and glue in the spacer as before. After the first spacer is in place and dry, place the concave side of the objective lens flush against it, and put the other spacer snugly against the lens to hold it in place (again using the drill - glue method). Now there are two pieces, each containing one of the lenses. Slide the mailing tubes together as shown in the drawing above, and the telescope is done. By leaving these two pieces unglued, the telescope may be focused simply by sliding the eyepiece part inside the objective part. After a desired magnification/focus is found, the two pieces may be permanently attached (or some tape will give a semi-permanent attachment). Two images of a finished tube are shown below. The first picture shows the telescope tube from the objective side while the second image shows the ocular end of the tube: Making the Mounting: This Year's Work For the first half of the semester, we used the mountings built by last year's group. It looked like this: This image was produced by the star jumping in the field of view. We tried to have one person hold the telescope tube steady, but it takes very little movement to cause a star to move across the field of view when the field of view is only about 15 arc minutes. Moreover, our telescope would blow over often and required one person to hold it as still as possible, but this never really worked very well. So, we built a new mounting and stars looked like this, with very little distortion. The new mounting was constructed on a Saturday morning and afternoon, based on plans by Tom Williams. It looks like this: This telescope mounting is composed of a base a support box for the telescope tubing and its bracket assembly a bracket assembly encasing the telescope tubing with trunnion bearings which fit into the trunnion notch plates attached to the inside of the support box Parts List: Polybutylene Pipe Diameter = 4", Length = approximately 5' These can vary. The length is approximately equal to the height that you desire. Polybutylene pipe for the trunnion (swivel) for the telescope tubing Diameter = 2", Length = approximately 2 pieces about 1" long This is glued to the tube bracket assembly with Wood glue Plastic furniture tacks These are used to stick into the bottom of the legs of chairs to protect the floor. They provide the foundation for the trunnions to turn. Wing Screws These are used for the end plates of the tube bracket assembly. They allow for the different telescopes to be used, just by unscrewing these and inserting a different telescope. Plastic floor flanges which can hold the big tubing and be nailed to the wood Nails, Bolts, Screws A whole lot of plywood! Suggested Tools: Power Saw circular saw Power Drill glue work bench to cut out various shapes of wood Instructions: The base is constructed by attaching the plastic holder to a square piece of plywood and then adding four legs which extend outward. The big plastic tubing can be glued into the holder. At the top of the tubing, another plastic holder is put on, but not glued, so that the entire top of the mounting can be removed for adjustments and travel purposes. The top plastic holder is attached to a round piece of plywood which has a whole cut out of the middle and a screw inserted there. The support box will be attached here and can swivel 360 degrees. The support box is constructed much like a shoe box except that one side is missing. The bottom has a rectangle cut out of end (see where Travis's hand is). This allows the bracket assembly to rotate all the way to a position perpendicular to the ground. Also, on the end of the box opposite Travis, cut out a semicircle to allow the telescope to rotate all the way to a position parallel to the ground. The bracket assembly encases the telescope. It looks like this: It is made up of a rectangular three-sided box with end plates on either end (bottom). The end plates (at the top) have wing screws which allow the top half of the end plate to be removed from the tube bracket assembly, releasing the telescope. This is useful for making adjustments to the telescope itself or for using a different powered telescope in the same mounting. Notice also the round wooden pieces attached to either side of the support box in the above picture. Wood glue is applied around the circumference of the circle and the smaller plastic tubes, only about an inch in length, are squeezed on. These are the trunnions. The unique part of the mounting is the trunnion. Trunnion notch plates are attached to the insides of the left and right walls (when looking through the telescope) of the support box. Plastic Furniture tacks are stuck into the insides of the triangular cut-out and support the trunnions. These tacks can be moved at any time to increase or decrease friction so that the trunnions will move smoothly, but also not allow the tube bracket assembly (and thus the telescope) to slip. The tube bracket assembly, telescope, and support box combined can be removed from the base. The result is that our telescope moves freely through an entire hemisphere giving us the ability to look at anything in the sky. It was with this mounting that we were finally able to recreate some of Galileo's observations. If you would like more information on how to build a relatively cheap mounting for your Galilean telescope, just e-mail Tom Williams or Jessica Williams. Return to the astronomy group's home page .

If you would like more information on how to build a relatively cheap mounting for your Galilean telescope, just e-mail Tom Williams or Jessica Williams. Return to the astronomy group's home page .

Place the eyepiece flush (flat side) against the inside of this eyehole. The large piece of the inner mailing tube left will be used to hold this in place. To do this, drill small holes around the outside of the eyepiece tube. Then, with the eyepiece properly in place, slide the inner tube into it, put glue into the holes, and turn the tube a little bit to spread the glue inside. Hold the tube snugly against the lens inside the cap until the glue dries. Now, put this aside and take the large outer tube and the two spacers cut from the inner tube. Cut the closed end off of the outer tube, then use the other end to mount the objective lens (since that end already has a clean cut). Again, the "drill holes - put in glue" technique will be used to hold the spacers in place. First, check how far the inner spacer needs to be placed inside the tube so that the lens and other spacer will be able to sit inside the tube comfortably. Then drill holes in the outer tube around this area and glue in the spacer as before. After the first spacer is in place and dry, place the concave side of the objective lens flush against it, and put the other spacer snugly against the lens to hold it in place (again using the drill - glue method). Now there are two pieces, each containing one of the lenses. Slide the mailing tubes together as shown in the drawing above, and the telescope is done. By leaving these two pieces unglued, the telescope may be focused simply by sliding the eyepiece part inside the objective part. After a desired magnification/focus is found, the two pieces may be permanently attached (or some tape will give a semi-permanent attachment). Two images of a finished tube are shown below. The first picture shows the telescope tube from the objective side while the second image shows the ocular end of the tube: Making the Mounting: This Year's Work For the first half of the semester, we used the mountings built by last year's group. It looked like this: This image was produced by the star jumping in the field of view. We tried to have one person hold the telescope tube steady, but it takes very little movement to cause a star to move across the field of view when the field of view is only about 15 arc minutes. Moreover, our telescope would blow over often and required one person to hold it as still as possible, but this never really worked very well. So, we built a new mounting and stars looked like this, with very little distortion. The new mounting was constructed on a Saturday morning and afternoon, based on plans by Tom Williams. It looks like this: This telescope mounting is composed of a base a support box for the telescope tubing and its bracket assembly a bracket assembly encasing the telescope tubing with trunnion bearings which fit into the trunnion notch plates attached to the inside of the support box Parts List: Polybutylene Pipe Diameter = 4", Length = approximately 5' These can vary. The length is approximately equal to the height that you desire. Polybutylene pipe for the trunnion (swivel) for the telescope tubing Diameter = 2", Length = approximately 2 pieces about 1" long This is glued to the tube bracket assembly with Wood glue Plastic furniture tacks These are used to stick into the bottom of the legs of chairs to protect the floor. They provide the foundation for the trunnions to turn. Wing Screws These are used for the end plates of the tube bracket assembly. They allow for the different telescopes to be used, just by unscrewing these and inserting a different telescope. Plastic floor flanges which can hold the big tubing and be nailed to the wood Nails, Bolts, Screws A whole lot of plywood! Suggested Tools: Power Saw circular saw Power Drill glue work bench to cut out various shapes of wood Instructions: The base is constructed by attaching the plastic holder to a square piece of plywood and then adding four legs which extend outward. The big plastic tubing can be glued into the holder. At the top of the tubing, another plastic holder is put on, but not glued, so that the entire top of the mounting can be removed for adjustments and travel purposes. The top plastic holder is attached to a round piece of plywood which has a whole cut out of the middle and a screw inserted there. The support box will be attached here and can swivel 360 degrees. The support box is constructed much like a shoe box except that one side is missing. The bottom has a rectangle cut out of end (see where Travis's hand is). This allows the bracket assembly to rotate all the way to a position perpendicular to the ground. Also, on the end of the box opposite Travis, cut out a semicircle to allow the telescope to rotate all the way to a position parallel to the ground. The bracket assembly encases the telescope. It looks like this: It is made up of a rectangular three-sided box with end plates on either end (bottom). The end plates (at the top) have wing screws which allow the top half of the end plate to be removed from the tube bracket assembly, releasing the telescope. This is useful for making adjustments to the telescope itself or for using a different powered telescope in the same mounting. Notice also the round wooden pieces attached to either side of the support box in the above picture. Wood glue is applied around the circumference of the circle and the smaller plastic tubes, only about an inch in length, are squeezed on. These are the trunnions. The unique part of the mounting is the trunnion. Trunnion notch plates are attached to the insides of the left and right walls (when looking through the telescope) of the support box. Plastic Furniture tacks are stuck into the insides of the triangular cut-out and support the trunnions. These tacks can be moved at any time to increase or decrease friction so that the trunnions will move smoothly, but also not allow the tube bracket assembly (and thus the telescope) to slip. The tube bracket assembly, telescope, and support box combined can be removed from the base. The result is that our telescope moves freely through an entire hemisphere giving us the ability to look at anything in the sky. It was with this mounting that we were finally able to recreate some of Galileo's observations. If you would like more information on how to build a relatively cheap mounting for your Galilean telescope, just e-mail Tom Williams or Jessica Williams. Return to the astronomy group's home page .

Reflection gratings are used in spectroscopy to study the spectral lines of various materials, in optical communications to multiplex or demultiplex signals, and in laser systems to produce a spectrum of light. The advantages of reflection gratings include high efficiency, high accuracy, and the ability to operate in a wide range of environmental conditions. However, reflection gratings also have disadvantages, such as limited transmission, high reflection loss, and the need for accurate alignment.

The tube bracket assembly, telescope, and support box combined can be removed from the base. The result is that our telescope moves freely through an entire hemisphere giving us the ability to look at anything in the sky. It was with this mounting that we were finally able to recreate some of Galileo's observations. If you would like more information on how to build a relatively cheap mounting for your Galilean telescope, just e-mail Tom Williams or Jessica Williams. Return to the astronomy group's home page .

Limited Light Efficiency: Diffraction gratings can be less efficient than other types of spectroscopy equipment, as some of the light is lost as it diffracts through the grating.

After the first spacer is in place and dry, place the concave side of the objective lens flush against it, and put the other spacer snugly against the lens to hold it in place (again using the drill - glue method). Now there are two pieces, each containing one of the lenses. Slide the mailing tubes together as shown in the drawing above, and the telescope is done. By leaving these two pieces unglued, the telescope may be focused simply by sliding the eyepiece part inside the objective part. After a desired magnification/focus is found, the two pieces may be permanently attached (or some tape will give a semi-permanent attachment). Two images of a finished tube are shown below. The first picture shows the telescope tube from the objective side while the second image shows the ocular end of the tube: Making the Mounting: This Year's Work For the first half of the semester, we used the mountings built by last year's group. It looked like this: This image was produced by the star jumping in the field of view. We tried to have one person hold the telescope tube steady, but it takes very little movement to cause a star to move across the field of view when the field of view is only about 15 arc minutes. Moreover, our telescope would blow over often and required one person to hold it as still as possible, but this never really worked very well. So, we built a new mounting and stars looked like this, with very little distortion. The new mounting was constructed on a Saturday morning and afternoon, based on plans by Tom Williams. It looks like this: This telescope mounting is composed of a base a support box for the telescope tubing and its bracket assembly a bracket assembly encasing the telescope tubing with trunnion bearings which fit into the trunnion notch plates attached to the inside of the support box Parts List: Polybutylene Pipe Diameter = 4", Length = approximately 5' These can vary. The length is approximately equal to the height that you desire. Polybutylene pipe for the trunnion (swivel) for the telescope tubing Diameter = 2", Length = approximately 2 pieces about 1" long This is glued to the tube bracket assembly with Wood glue Plastic furniture tacks These are used to stick into the bottom of the legs of chairs to protect the floor. They provide the foundation for the trunnions to turn. Wing Screws These are used for the end plates of the tube bracket assembly. They allow for the different telescopes to be used, just by unscrewing these and inserting a different telescope. Plastic floor flanges which can hold the big tubing and be nailed to the wood Nails, Bolts, Screws A whole lot of plywood! Suggested Tools: Power Saw circular saw Power Drill glue work bench to cut out various shapes of wood Instructions: The base is constructed by attaching the plastic holder to a square piece of plywood and then adding four legs which extend outward. The big plastic tubing can be glued into the holder. At the top of the tubing, another plastic holder is put on, but not glued, so that the entire top of the mounting can be removed for adjustments and travel purposes. The top plastic holder is attached to a round piece of plywood which has a whole cut out of the middle and a screw inserted there. The support box will be attached here and can swivel 360 degrees. The support box is constructed much like a shoe box except that one side is missing. The bottom has a rectangle cut out of end (see where Travis's hand is). This allows the bracket assembly to rotate all the way to a position perpendicular to the ground. Also, on the end of the box opposite Travis, cut out a semicircle to allow the telescope to rotate all the way to a position parallel to the ground. The bracket assembly encases the telescope. It looks like this: It is made up of a rectangular three-sided box with end plates on either end (bottom). The end plates (at the top) have wing screws which allow the top half of the end plate to be removed from the tube bracket assembly, releasing the telescope. This is useful for making adjustments to the telescope itself or for using a different powered telescope in the same mounting. Notice also the round wooden pieces attached to either side of the support box in the above picture. Wood glue is applied around the circumference of the circle and the smaller plastic tubes, only about an inch in length, are squeezed on. These are the trunnions. The unique part of the mounting is the trunnion. Trunnion notch plates are attached to the insides of the left and right walls (when looking through the telescope) of the support box. Plastic Furniture tacks are stuck into the insides of the triangular cut-out and support the trunnions. These tacks can be moved at any time to increase or decrease friction so that the trunnions will move smoothly, but also not allow the tube bracket assembly (and thus the telescope) to slip. The tube bracket assembly, telescope, and support box combined can be removed from the base. The result is that our telescope moves freely through an entire hemisphere giving us the ability to look at anything in the sky. It was with this mounting that we were finally able to recreate some of Galileo's observations. If you would like more information on how to build a relatively cheap mounting for your Galilean telescope, just e-mail Tom Williams or Jessica Williams. Return to the astronomy group's home page .

"When there are no glasses in the tube, the rays proceed to the object FG along the straight lines ECF and EDG, but with the glasses put in they proceed along the refracted lines ECH and EDI. They are indeed squeezed together and where before, free, they were directed to the object FG, now they only grasp the part HI" Galileo, Sidereus Nuncius tr. Albert Van Helden, pp. 38-39. Actually, Galileo could not explain how his telescope magnified precisely. He did not understand, as we now know, that the magnification of his telescope can be computed by F/f (see top figure). Increasing the magnification requires lengthening the telescope. Our 10X telescope is about 4 feet long. From the above picture, you can see that an image, HI, will be viewed upright, making the Galilean telescope useful for terrestrial purposes as well as astronomical. Keplerian telescopes, in contrast, invert the image. What are the disadvantages of a Galilean telescope? The Galilean telescope's biggest disadvantage is its small field of view. A Galilean telescope typically has a field of view of about 15-18 arc minutes. The moon has a diameter of about 30 arc minutes, so the Galilean telescope only reveals approximately one-fourth of the moon's surface at one time. In the Houston skies, a typical field of view has only one star or no stars at all. This makes it very difficult to map a constellation. Increasing the magnification on the Galilean telescope, like all telescopes, reduces the field of view. Perhaps Galileo built a 30X telescope, but it is doubtful that he used much in his observations. The field of view must have been very tiny. How do you make a Galilean telescope?Building the Telescope Tube: Last Year's Group's Work Parts List (With approximate cost): Cardboard Telescoping Mailing Tube (1), $3 Diameter = 50mm (or 2"), Length = 1100mm (or 143") Should be comprised of an inner and outer tube with closed ends on the outer tube. Concave Convex Lens (the "objective lens") (1), $16 for this and the next lens as a pair. Focal Length = 1350mm (0.75 diopter) Cut to our specification of 49mm diameter. Plano Concave Lens (the "eyepiece") (1) Focal Length = -152mm (-6.6 diopter), Diameter = 49mm Cut to our specification of 49mm diameter. Suggested Tools: Coping Saw Alternatively, any other instrument that will make a relatively clean cut through the mailing tube. Drill (bit sizes discussed below) Super Glue Alternatively, any other kind of glue that will firmly hold the inner and outer mailing tubes together. It must be of a thin consistency. Greenlee Punch (optional) Instructions: The basic premise of the telescope tube is to align two lenses the appropriate distance from each other. For this telescope, the lenses are a concave convex (one side curved out and the other curved in) and a plano concave (one flat side and one side curved in). The plano concave lens is used as the "eyepiece" with the plano (flat) side facing the eye. The concave convex is used as the "objective lens" that is aligned with the eyepiece and with the convex side facing the sky. Notice that this lens is actually different than the plano convex lens used in the original Galilean telescope, but still gives the same results. The following design uses pieces of the inner tube of the mailing tube to hold the lenses in place inside the outer tube. This is best illustrated in the following diagram, which shows the cross section of the telescope tube: The outer tube of the mailing tube should have a short end that pulls off, and this can be used for the split in the outer tube shown above. This end will be used to hold the eyepiece. The inner tube must have two pieces (about 1" to 1.5" each) cut off of it that will be used as spacers to hold the objective lens in place. Make these cuts as straight and clean as possible, which will be difficult since the tube is made out of cardboard. A coping saw works pretty well for this. Take the short piece of the outer tube and cut or drill a hole (from 3/16" to 5/16" should be fine) directly in the center of the metal cap on the end. This will be the eyehole. It is important that this hole be as clean as possible (no metal protrusions) so that the the flat side of the eyepiece will fit snugly against the metal cap. An electrician's hole punch or Greenlee Punch works well for this task. If a drill is used, drill with a light pressure, then smooth out the inside surface as much as possible. Place the eyepiece flush (flat side) against the inside of this eyehole. The large piece of the inner mailing tube left will be used to hold this in place. To do this, drill small holes around the outside of the eyepiece tube. Then, with the eyepiece properly in place, slide the inner tube into it, put glue into the holes, and turn the tube a little bit to spread the glue inside. Hold the tube snugly against the lens inside the cap until the glue dries. Now, put this aside and take the large outer tube and the two spacers cut from the inner tube. Cut the closed end off of the outer tube, then use the other end to mount the objective lens (since that end already has a clean cut). Again, the "drill holes - put in glue" technique will be used to hold the spacers in place. First, check how far the inner spacer needs to be placed inside the tube so that the lens and other spacer will be able to sit inside the tube comfortably. Then drill holes in the outer tube around this area and glue in the spacer as before. After the first spacer is in place and dry, place the concave side of the objective lens flush against it, and put the other spacer snugly against the lens to hold it in place (again using the drill - glue method). Now there are two pieces, each containing one of the lenses. Slide the mailing tubes together as shown in the drawing above, and the telescope is done. By leaving these two pieces unglued, the telescope may be focused simply by sliding the eyepiece part inside the objective part. After a desired magnification/focus is found, the two pieces may be permanently attached (or some tape will give a semi-permanent attachment). Two images of a finished tube are shown below. The first picture shows the telescope tube from the objective side while the second image shows the ocular end of the tube: Making the Mounting: This Year's Work For the first half of the semester, we used the mountings built by last year's group. It looked like this: This image was produced by the star jumping in the field of view. We tried to have one person hold the telescope tube steady, but it takes very little movement to cause a star to move across the field of view when the field of view is only about 15 arc minutes. Moreover, our telescope would blow over often and required one person to hold it as still as possible, but this never really worked very well. So, we built a new mounting and stars looked like this, with very little distortion. The new mounting was constructed on a Saturday morning and afternoon, based on plans by Tom Williams. It looks like this: This telescope mounting is composed of a base a support box for the telescope tubing and its bracket assembly a bracket assembly encasing the telescope tubing with trunnion bearings which fit into the trunnion notch plates attached to the inside of the support box Parts List: Polybutylene Pipe Diameter = 4", Length = approximately 5' These can vary. The length is approximately equal to the height that you desire. Polybutylene pipe for the trunnion (swivel) for the telescope tubing Diameter = 2", Length = approximately 2 pieces about 1" long This is glued to the tube bracket assembly with Wood glue Plastic furniture tacks These are used to stick into the bottom of the legs of chairs to protect the floor. They provide the foundation for the trunnions to turn. Wing Screws These are used for the end plates of the tube bracket assembly. They allow for the different telescopes to be used, just by unscrewing these and inserting a different telescope. Plastic floor flanges which can hold the big tubing and be nailed to the wood Nails, Bolts, Screws A whole lot of plywood! Suggested Tools: Power Saw circular saw Power Drill glue work bench to cut out various shapes of wood Instructions: The base is constructed by attaching the plastic holder to a square piece of plywood and then adding four legs which extend outward. The big plastic tubing can be glued into the holder. At the top of the tubing, another plastic holder is put on, but not glued, so that the entire top of the mounting can be removed for adjustments and travel purposes. The top plastic holder is attached to a round piece of plywood which has a whole cut out of the middle and a screw inserted there. The support box will be attached here and can swivel 360 degrees. The support box is constructed much like a shoe box except that one side is missing. The bottom has a rectangle cut out of end (see where Travis's hand is). This allows the bracket assembly to rotate all the way to a position perpendicular to the ground. Also, on the end of the box opposite Travis, cut out a semicircle to allow the telescope to rotate all the way to a position parallel to the ground. The bracket assembly encases the telescope. It looks like this: It is made up of a rectangular three-sided box with end plates on either end (bottom). The end plates (at the top) have wing screws which allow the top half of the end plate to be removed from the tube bracket assembly, releasing the telescope. This is useful for making adjustments to the telescope itself or for using a different powered telescope in the same mounting. Notice also the round wooden pieces attached to either side of the support box in the above picture. Wood glue is applied around the circumference of the circle and the smaller plastic tubes, only about an inch in length, are squeezed on. These are the trunnions. The unique part of the mounting is the trunnion. Trunnion notch plates are attached to the insides of the left and right walls (when looking through the telescope) of the support box. Plastic Furniture tacks are stuck into the insides of the triangular cut-out and support the trunnions. These tacks can be moved at any time to increase or decrease friction so that the trunnions will move smoothly, but also not allow the tube bracket assembly (and thus the telescope) to slip. The tube bracket assembly, telescope, and support box combined can be removed from the base. The result is that our telescope moves freely through an entire hemisphere giving us the ability to look at anything in the sky. It was with this mounting that we were finally able to recreate some of Galileo's observations. If you would like more information on how to build a relatively cheap mounting for your Galilean telescope, just e-mail Tom Williams or Jessica Williams. Return to the astronomy group's home page .

The concept of diffraction gratings is based on the principle of diffraction, which is the spreading out of light as it passes through a small aperture or grating. When light passes through the grating, it diffracts and produces an interference pattern. The distance between the diffracted waves is determined by the wavelength of the light, allowing light to be separated into its component wavelengths.

Diffraction gratings are optical components that are widely used in various scientific and technological applications. They are made up of a series of closely spaced parallel lines or grooves engraved on a surface, which diffract light and split it into its component wavelengths. This results in the creation of a spectrum, which is a visual representation of light separated into its individual wavelengths.

Overall, holographic diffraction gratings are a valuable component in various optical systems and applications, such as spectroscopy, optical communications, laser systems, and imaging. They offer high diffraction efficiency, high spatial frequency, and versatility, making them a versatile and valuable component in many optical systems.

Diffractiongrating formula

Versatility: Diffraction gratings can be made from a variety of materials, including glass, plastic, and metal, and can be fabricated using a variety of techniques, such as holographic, e-beam, and laser lithography methods.

Diffraction gratings were first described by James Gregory in 1663, and they were later experimentally verified by Thomas Young in 1801. In the early days, gratings were made by hand, and they were used primarily in spectroscopy to study the spectral lines of various materials. The use of diffraction gratings in spectroscopy was limited by the low efficiency and low accuracy of the gratings, which were produced by manual labor. In the mid-19th century, the development of photographic methods for producing gratings enabled the production of high-efficiency gratings with higher accuracy. Since then, diffraction gratings have been widely used in a variety of applications, including spectroscopy, optical communications, and laser systems.

Transmission gratings are used in spectroscopy to study the spectral lines of various materials, in optical communications to multiplex or demultiplex signals, and in laser systems to produce a spectrum of light. The advantages of transmission gratings include high efficiency, low loss, and the ability to combine or separate light with high accuracy. However, transmission gratings are also susceptible to environmental effects, such as temperature and pressure, which can affect their performance.

A holographic diffraction grating is a type of diffraction grating that is made by the process of holography. Holography is a technique for producing a three-dimensional image by recording the interference pattern of light waves. The holographic diffraction grating is produced by exposing a photosensitive material, such as film or a photopolymer, to the interference pattern of two laser beams. The resulting interference pattern forms a grating on the surface of the material, with the lines or grooves of the grating representing the diffraction information of the light.

In the late 19th century, the production of diffraction gratings became more sophisticated and efficient, with the development of new technologies and materials. The first holographic diffraction grating was invented in the 1960s, and it revolutionized the field of diffraction gratings, as it allowed for the production of gratings with high diffraction efficiency and improved spectral resolution.

Diffraction gratingsexamples

Require Alignment: Diffraction gratings must be carefully aligned in order to produce accurate spectra. This can be time-consuming and requires a high degree of precision.

Reflection gratings are made of a reflective material and are designed to reflect light back to the observer. The light waves diffract at the lines or grooves of the grating, producing a diffraction pattern that consists of a series of bright and dark bands. The diffracted light forms a series of diffraction orders, each corresponding to a specific diffraction angle, which is equal to the angle of incidence.

Transmission gratings are made of a transparent material and are designed to transmit light through the grating. The light waves diffract, or bend, at the lines or grooves of the grating, producing a diffraction pattern that consists of a series of bright and dark bands. The diffracted light forms a series of diffraction orders, each corresponding to a specific diffraction angle, which depends on the grating spacing, the wavelength of light, and the angle of incidence.

The basic premise of the telescope tube is to align two lenses the appropriate distance from each other. For this telescope, the lenses are a concave convex (one side curved out and the other curved in) and a plano concave (one flat side and one side curved in). The plano concave lens is used as the "eyepiece" with the plano (flat) side facing the eye. The concave convex is used as the "objective lens" that is aligned with the eyepiece and with the convex side facing the sky. Notice that this lens is actually different than the plano convex lens used in the original Galilean telescope, but still gives the same results. The following design uses pieces of the inner tube of the mailing tube to hold the lenses in place inside the outer tube. This is best illustrated in the following diagram, which shows the cross section of the telescope tube: The outer tube of the mailing tube should have a short end that pulls off, and this can be used for the split in the outer tube shown above. This end will be used to hold the eyepiece. The inner tube must have two pieces (about 1" to 1.5" each) cut off of it that will be used as spacers to hold the objective lens in place. Make these cuts as straight and clean as possible, which will be difficult since the tube is made out of cardboard. A coping saw works pretty well for this. Take the short piece of the outer tube and cut or drill a hole (from 3/16" to 5/16" should be fine) directly in the center of the metal cap on the end. This will be the eyehole. It is important that this hole be as clean as possible (no metal protrusions) so that the the flat side of the eyepiece will fit snugly against the metal cap. An electrician's hole punch or Greenlee Punch works well for this task. If a drill is used, drill with a light pressure, then smooth out the inside surface as much as possible. Place the eyepiece flush (flat side) against the inside of this eyehole. The large piece of the inner mailing tube left will be used to hold this in place. To do this, drill small holes around the outside of the eyepiece tube. Then, with the eyepiece properly in place, slide the inner tube into it, put glue into the holes, and turn the tube a little bit to spread the glue inside. Hold the tube snugly against the lens inside the cap until the glue dries. Now, put this aside and take the large outer tube and the two spacers cut from the inner tube. Cut the closed end off of the outer tube, then use the other end to mount the objective lens (since that end already has a clean cut). Again, the "drill holes - put in glue" technique will be used to hold the spacers in place. First, check how far the inner spacer needs to be placed inside the tube so that the lens and other spacer will be able to sit inside the tube comfortably. Then drill holes in the outer tube around this area and glue in the spacer as before. After the first spacer is in place and dry, place the concave side of the objective lens flush against it, and put the other spacer snugly against the lens to hold it in place (again using the drill - glue method). Now there are two pieces, each containing one of the lenses. Slide the mailing tubes together as shown in the drawing above, and the telescope is done. By leaving these two pieces unglued, the telescope may be focused simply by sliding the eyepiece part inside the objective part. After a desired magnification/focus is found, the two pieces may be permanently attached (or some tape will give a semi-permanent attachment). Two images of a finished tube are shown below. The first picture shows the telescope tube from the objective side while the second image shows the ocular end of the tube: Making the Mounting: This Year's Work For the first half of the semester, we used the mountings built by last year's group. It looked like this: This image was produced by the star jumping in the field of view. We tried to have one person hold the telescope tube steady, but it takes very little movement to cause a star to move across the field of view when the field of view is only about 15 arc minutes. Moreover, our telescope would blow over often and required one person to hold it as still as possible, but this never really worked very well. So, we built a new mounting and stars looked like this, with very little distortion. The new mounting was constructed on a Saturday morning and afternoon, based on plans by Tom Williams. It looks like this: This telescope mounting is composed of a base a support box for the telescope tubing and its bracket assembly a bracket assembly encasing the telescope tubing with trunnion bearings which fit into the trunnion notch plates attached to the inside of the support box Parts List: Polybutylene Pipe Diameter = 4", Length = approximately 5' These can vary. The length is approximately equal to the height that you desire. Polybutylene pipe for the trunnion (swivel) for the telescope tubing Diameter = 2", Length = approximately 2 pieces about 1" long This is glued to the tube bracket assembly with Wood glue Plastic furniture tacks These are used to stick into the bottom of the legs of chairs to protect the floor. They provide the foundation for the trunnions to turn. Wing Screws These are used for the end plates of the tube bracket assembly. They allow for the different telescopes to be used, just by unscrewing these and inserting a different telescope. Plastic floor flanges which can hold the big tubing and be nailed to the wood Nails, Bolts, Screws A whole lot of plywood! Suggested Tools: Power Saw circular saw Power Drill glue work bench to cut out various shapes of wood Instructions: The base is constructed by attaching the plastic holder to a square piece of plywood and then adding four legs which extend outward. The big plastic tubing can be glued into the holder. At the top of the tubing, another plastic holder is put on, but not glued, so that the entire top of the mounting can be removed for adjustments and travel purposes. The top plastic holder is attached to a round piece of plywood which has a whole cut out of the middle and a screw inserted there. The support box will be attached here and can swivel 360 degrees. The support box is constructed much like a shoe box except that one side is missing. The bottom has a rectangle cut out of end (see where Travis's hand is). This allows the bracket assembly to rotate all the way to a position perpendicular to the ground. Also, on the end of the box opposite Travis, cut out a semicircle to allow the telescope to rotate all the way to a position parallel to the ground. The bracket assembly encases the telescope. It looks like this: It is made up of a rectangular three-sided box with end plates on either end (bottom). The end plates (at the top) have wing screws which allow the top half of the end plate to be removed from the tube bracket assembly, releasing the telescope. This is useful for making adjustments to the telescope itself or for using a different powered telescope in the same mounting. Notice also the round wooden pieces attached to either side of the support box in the above picture. Wood glue is applied around the circumference of the circle and the smaller plastic tubes, only about an inch in length, are squeezed on. These are the trunnions. The unique part of the mounting is the trunnion. Trunnion notch plates are attached to the insides of the left and right walls (when looking through the telescope) of the support box. Plastic Furniture tacks are stuck into the insides of the triangular cut-out and support the trunnions. These tacks can be moved at any time to increase or decrease friction so that the trunnions will move smoothly, but also not allow the tube bracket assembly (and thus the telescope) to slip. The tube bracket assembly, telescope, and support box combined can be removed from the base. The result is that our telescope moves freely through an entire hemisphere giving us the ability to look at anything in the sky. It was with this mounting that we were finally able to recreate some of Galileo's observations. If you would like more information on how to build a relatively cheap mounting for your Galilean telescope, just e-mail Tom Williams or Jessica Williams. Return to the astronomy group's home page .

The outer tube of the mailing tube should have a short end that pulls off, and this can be used for the split in the outer tube shown above. This end will be used to hold the eyepiece. The inner tube must have two pieces (about 1" to 1.5" each) cut off of it that will be used as spacers to hold the objective lens in place. Make these cuts as straight and clean as possible, which will be difficult since the tube is made out of cardboard. A coping saw works pretty well for this. Take the short piece of the outer tube and cut or drill a hole (from 3/16" to 5/16" should be fine) directly in the center of the metal cap on the end. This will be the eyehole. It is important that this hole be as clean as possible (no metal protrusions) so that the the flat side of the eyepiece will fit snugly against the metal cap. An electrician's hole punch or Greenlee Punch works well for this task. If a drill is used, drill with a light pressure, then smooth out the inside surface as much as possible. Place the eyepiece flush (flat side) against the inside of this eyehole. The large piece of the inner mailing tube left will be used to hold this in place. To do this, drill small holes around the outside of the eyepiece tube. Then, with the eyepiece properly in place, slide the inner tube into it, put glue into the holes, and turn the tube a little bit to spread the glue inside. Hold the tube snugly against the lens inside the cap until the glue dries. Now, put this aside and take the large outer tube and the two spacers cut from the inner tube. Cut the closed end off of the outer tube, then use the other end to mount the objective lens (since that end already has a clean cut). Again, the "drill holes - put in glue" technique will be used to hold the spacers in place. First, check how far the inner spacer needs to be placed inside the tube so that the lens and other spacer will be able to sit inside the tube comfortably. Then drill holes in the outer tube around this area and glue in the spacer as before. After the first spacer is in place and dry, place the concave side of the objective lens flush against it, and put the other spacer snugly against the lens to hold it in place (again using the drill - glue method). Now there are two pieces, each containing one of the lenses. Slide the mailing tubes together as shown in the drawing above, and the telescope is done. By leaving these two pieces unglued, the telescope may be focused simply by sliding the eyepiece part inside the objective part. After a desired magnification/focus is found, the two pieces may be permanently attached (or some tape will give a semi-permanent attachment). Two images of a finished tube are shown below. The first picture shows the telescope tube from the objective side while the second image shows the ocular end of the tube: Making the Mounting: This Year's Work For the first half of the semester, we used the mountings built by last year's group. It looked like this: This image was produced by the star jumping in the field of view. We tried to have one person hold the telescope tube steady, but it takes very little movement to cause a star to move across the field of view when the field of view is only about 15 arc minutes. Moreover, our telescope would blow over often and required one person to hold it as still as possible, but this never really worked very well. So, we built a new mounting and stars looked like this, with very little distortion. The new mounting was constructed on a Saturday morning and afternoon, based on plans by Tom Williams. It looks like this: This telescope mounting is composed of a base a support box for the telescope tubing and its bracket assembly a bracket assembly encasing the telescope tubing with trunnion bearings which fit into the trunnion notch plates attached to the inside of the support box Parts List: Polybutylene Pipe Diameter = 4", Length = approximately 5' These can vary. The length is approximately equal to the height that you desire. Polybutylene pipe for the trunnion (swivel) for the telescope tubing Diameter = 2", Length = approximately 2 pieces about 1" long This is glued to the tube bracket assembly with Wood glue Plastic furniture tacks These are used to stick into the bottom of the legs of chairs to protect the floor. They provide the foundation for the trunnions to turn. Wing Screws These are used for the end plates of the tube bracket assembly. They allow for the different telescopes to be used, just by unscrewing these and inserting a different telescope. Plastic floor flanges which can hold the big tubing and be nailed to the wood Nails, Bolts, Screws A whole lot of plywood! Suggested Tools: Power Saw circular saw Power Drill glue work bench to cut out various shapes of wood Instructions: The base is constructed by attaching the plastic holder to a square piece of plywood and then adding four legs which extend outward. The big plastic tubing can be glued into the holder. At the top of the tubing, another plastic holder is put on, but not glued, so that the entire top of the mounting can be removed for adjustments and travel purposes. The top plastic holder is attached to a round piece of plywood which has a whole cut out of the middle and a screw inserted there. The support box will be attached here and can swivel 360 degrees. The support box is constructed much like a shoe box except that one side is missing. The bottom has a rectangle cut out of end (see where Travis's hand is). This allows the bracket assembly to rotate all the way to a position perpendicular to the ground. Also, on the end of the box opposite Travis, cut out a semicircle to allow the telescope to rotate all the way to a position parallel to the ground. The bracket assembly encases the telescope. It looks like this: It is made up of a rectangular three-sided box with end plates on either end (bottom). The end plates (at the top) have wing screws which allow the top half of the end plate to be removed from the tube bracket assembly, releasing the telescope. This is useful for making adjustments to the telescope itself or for using a different powered telescope in the same mounting. Notice also the round wooden pieces attached to either side of the support box in the above picture. Wood glue is applied around the circumference of the circle and the smaller plastic tubes, only about an inch in length, are squeezed on. These are the trunnions. The unique part of the mounting is the trunnion. Trunnion notch plates are attached to the insides of the left and right walls (when looking through the telescope) of the support box. Plastic Furniture tacks are stuck into the insides of the triangular cut-out and support the trunnions. These tacks can be moved at any time to increase or decrease friction so that the trunnions will move smoothly, but also not allow the tube bracket assembly (and thus the telescope) to slip. The tube bracket assembly, telescope, and support box combined can be removed from the base. The result is that our telescope moves freely through an entire hemisphere giving us the ability to look at anything in the sky. It was with this mounting that we were finally able to recreate some of Galileo's observations. If you would like more information on how to build a relatively cheap mounting for your Galilean telescope, just e-mail Tom Williams or Jessica Williams. Return to the astronomy group's home page .

Henry A rowland in 1884 with the first machine made for mass producing diffraction gratings. The engine ruled a large number of closely spaced lines on a metal surface.

So, we built a new mounting and stars looked like this, with very little distortion. The new mounting was constructed on a Saturday morning and afternoon, based on plans by Tom Williams. It looks like this: This telescope mounting is composed of a base a support box for the telescope tubing and its bracket assembly a bracket assembly encasing the telescope tubing with trunnion bearings which fit into the trunnion notch plates attached to the inside of the support box Parts List: Polybutylene Pipe Diameter = 4", Length = approximately 5' These can vary. The length is approximately equal to the height that you desire. Polybutylene pipe for the trunnion (swivel) for the telescope tubing Diameter = 2", Length = approximately 2 pieces about 1" long This is glued to the tube bracket assembly with Wood glue Plastic furniture tacks These are used to stick into the bottom of the legs of chairs to protect the floor. They provide the foundation for the trunnions to turn. Wing Screws These are used for the end plates of the tube bracket assembly. They allow for the different telescopes to be used, just by unscrewing these and inserting a different telescope. Plastic floor flanges which can hold the big tubing and be nailed to the wood Nails, Bolts, Screws A whole lot of plywood! Suggested Tools: Power Saw circular saw Power Drill glue work bench to cut out various shapes of wood Instructions: The base is constructed by attaching the plastic holder to a square piece of plywood and then adding four legs which extend outward. The big plastic tubing can be glued into the holder. At the top of the tubing, another plastic holder is put on, but not glued, so that the entire top of the mounting can be removed for adjustments and travel purposes. The top plastic holder is attached to a round piece of plywood which has a whole cut out of the middle and a screw inserted there. The support box will be attached here and can swivel 360 degrees. The support box is constructed much like a shoe box except that one side is missing. The bottom has a rectangle cut out of end (see where Travis's hand is). This allows the bracket assembly to rotate all the way to a position perpendicular to the ground. Also, on the end of the box opposite Travis, cut out a semicircle to allow the telescope to rotate all the way to a position parallel to the ground. The bracket assembly encases the telescope. It looks like this: It is made up of a rectangular three-sided box with end plates on either end (bottom). The end plates (at the top) have wing screws which allow the top half of the end plate to be removed from the tube bracket assembly, releasing the telescope. This is useful for making adjustments to the telescope itself or for using a different powered telescope in the same mounting. Notice also the round wooden pieces attached to either side of the support box in the above picture. Wood glue is applied around the circumference of the circle and the smaller plastic tubes, only about an inch in length, are squeezed on. These are the trunnions. The unique part of the mounting is the trunnion. Trunnion notch plates are attached to the insides of the left and right walls (when looking through the telescope) of the support box. Plastic Furniture tacks are stuck into the insides of the triangular cut-out and support the trunnions. These tacks can be moved at any time to increase or decrease friction so that the trunnions will move smoothly, but also not allow the tube bracket assembly (and thus the telescope) to slip. The tube bracket assembly, telescope, and support box combined can be removed from the base. The result is that our telescope moves freely through an entire hemisphere giving us the ability to look at anything in the sky. It was with this mounting that we were finally able to recreate some of Galileo's observations. If you would like more information on how to build a relatively cheap mounting for your Galilean telescope, just e-mail Tom Williams or Jessica Williams. Return to the astronomy group's home page .

Instructions: The base is constructed by attaching the plastic holder to a square piece of plywood and then adding four legs which extend outward. The big plastic tubing can be glued into the holder. At the top of the tubing, another plastic holder is put on, but not glued, so that the entire top of the mounting can be removed for adjustments and travel purposes. The top plastic holder is attached to a round piece of plywood which has a whole cut out of the middle and a screw inserted there. The support box will be attached here and can swivel 360 degrees. The support box is constructed much like a shoe box except that one side is missing. The bottom has a rectangle cut out of end (see where Travis's hand is). This allows the bracket assembly to rotate all the way to a position perpendicular to the ground. Also, on the end of the box opposite Travis, cut out a semicircle to allow the telescope to rotate all the way to a position parallel to the ground. The bracket assembly encases the telescope. It looks like this: It is made up of a rectangular three-sided box with end plates on either end (bottom). The end plates (at the top) have wing screws which allow the top half of the end plate to be removed from the tube bracket assembly, releasing the telescope. This is useful for making adjustments to the telescope itself or for using a different powered telescope in the same mounting. Notice also the round wooden pieces attached to either side of the support box in the above picture. Wood glue is applied around the circumference of the circle and the smaller plastic tubes, only about an inch in length, are squeezed on. These are the trunnions. The unique part of the mounting is the trunnion. Trunnion notch plates are attached to the insides of the left and right walls (when looking through the telescope) of the support box. Plastic Furniture tacks are stuck into the insides of the triangular cut-out and support the trunnions. These tacks can be moved at any time to increase or decrease friction so that the trunnions will move smoothly, but also not allow the tube bracket assembly (and thus the telescope) to slip. The tube bracket assembly, telescope, and support box combined can be removed from the base. The result is that our telescope moves freely through an entire hemisphere giving us the ability to look at anything in the sky. It was with this mounting that we were finally able to recreate some of Galileo's observations. If you would like more information on how to build a relatively cheap mounting for your Galilean telescope, just e-mail Tom Williams or Jessica Williams. Return to the astronomy group's home page .

Actually, Galileo could not explain how his telescope magnified precisely. He did not understand, as we now know, that the magnification of his telescope can be computed by F/f (see top figure). Increasing the magnification requires lengthening the telescope. Our 10X telescope is about 4 feet long. From the above picture, you can see that an image, HI, will be viewed upright, making the Galilean telescope useful for terrestrial purposes as well as astronomical. Keplerian telescopes, in contrast, invert the image. What are the disadvantages of a Galilean telescope? The Galilean telescope's biggest disadvantage is its small field of view. A Galilean telescope typically has a field of view of about 15-18 arc minutes. The moon has a diameter of about 30 arc minutes, so the Galilean telescope only reveals approximately one-fourth of the moon's surface at one time. In the Houston skies, a typical field of view has only one star or no stars at all. This makes it very difficult to map a constellation. Increasing the magnification on the Galilean telescope, like all telescopes, reduces the field of view. Perhaps Galileo built a 30X telescope, but it is doubtful that he used much in his observations. The field of view must have been very tiny. How do you make a Galilean telescope?Building the Telescope Tube: Last Year's Group's Work Parts List (With approximate cost): Cardboard Telescoping Mailing Tube (1), $3 Diameter = 50mm (or 2"), Length = 1100mm (or 143") Should be comprised of an inner and outer tube with closed ends on the outer tube. Concave Convex Lens (the "objective lens") (1), $16 for this and the next lens as a pair. Focal Length = 1350mm (0.75 diopter) Cut to our specification of 49mm diameter. Plano Concave Lens (the "eyepiece") (1) Focal Length = -152mm (-6.6 diopter), Diameter = 49mm Cut to our specification of 49mm diameter. Suggested Tools: Coping Saw Alternatively, any other instrument that will make a relatively clean cut through the mailing tube. Drill (bit sizes discussed below) Super Glue Alternatively, any other kind of glue that will firmly hold the inner and outer mailing tubes together. It must be of a thin consistency. Greenlee Punch (optional) Instructions: The basic premise of the telescope tube is to align two lenses the appropriate distance from each other. For this telescope, the lenses are a concave convex (one side curved out and the other curved in) and a plano concave (one flat side and one side curved in). The plano concave lens is used as the "eyepiece" with the plano (flat) side facing the eye. The concave convex is used as the "objective lens" that is aligned with the eyepiece and with the convex side facing the sky. Notice that this lens is actually different than the plano convex lens used in the original Galilean telescope, but still gives the same results. The following design uses pieces of the inner tube of the mailing tube to hold the lenses in place inside the outer tube. This is best illustrated in the following diagram, which shows the cross section of the telescope tube: The outer tube of the mailing tube should have a short end that pulls off, and this can be used for the split in the outer tube shown above. This end will be used to hold the eyepiece. The inner tube must have two pieces (about 1" to 1.5" each) cut off of it that will be used as spacers to hold the objective lens in place. Make these cuts as straight and clean as possible, which will be difficult since the tube is made out of cardboard. A coping saw works pretty well for this. Take the short piece of the outer tube and cut or drill a hole (from 3/16" to 5/16" should be fine) directly in the center of the metal cap on the end. This will be the eyehole. It is important that this hole be as clean as possible (no metal protrusions) so that the the flat side of the eyepiece will fit snugly against the metal cap. An electrician's hole punch or Greenlee Punch works well for this task. If a drill is used, drill with a light pressure, then smooth out the inside surface as much as possible. Place the eyepiece flush (flat side) against the inside of this eyehole. The large piece of the inner mailing tube left will be used to hold this in place. To do this, drill small holes around the outside of the eyepiece tube. Then, with the eyepiece properly in place, slide the inner tube into it, put glue into the holes, and turn the tube a little bit to spread the glue inside. Hold the tube snugly against the lens inside the cap until the glue dries. Now, put this aside and take the large outer tube and the two spacers cut from the inner tube. Cut the closed end off of the outer tube, then use the other end to mount the objective lens (since that end already has a clean cut). Again, the "drill holes - put in glue" technique will be used to hold the spacers in place. First, check how far the inner spacer needs to be placed inside the tube so that the lens and other spacer will be able to sit inside the tube comfortably. Then drill holes in the outer tube around this area and glue in the spacer as before. After the first spacer is in place and dry, place the concave side of the objective lens flush against it, and put the other spacer snugly against the lens to hold it in place (again using the drill - glue method). Now there are two pieces, each containing one of the lenses. Slide the mailing tubes together as shown in the drawing above, and the telescope is done. By leaving these two pieces unglued, the telescope may be focused simply by sliding the eyepiece part inside the objective part. After a desired magnification/focus is found, the two pieces may be permanently attached (or some tape will give a semi-permanent attachment). Two images of a finished tube are shown below. The first picture shows the telescope tube from the objective side while the second image shows the ocular end of the tube: Making the Mounting: This Year's Work For the first half of the semester, we used the mountings built by last year's group. It looked like this: This image was produced by the star jumping in the field of view. We tried to have one person hold the telescope tube steady, but it takes very little movement to cause a star to move across the field of view when the field of view is only about 15 arc minutes. Moreover, our telescope would blow over often and required one person to hold it as still as possible, but this never really worked very well. So, we built a new mounting and stars looked like this, with very little distortion. The new mounting was constructed on a Saturday morning and afternoon, based on plans by Tom Williams. It looks like this: This telescope mounting is composed of a base a support box for the telescope tubing and its bracket assembly a bracket assembly encasing the telescope tubing with trunnion bearings which fit into the trunnion notch plates attached to the inside of the support box Parts List: Polybutylene Pipe Diameter = 4", Length = approximately 5' These can vary. The length is approximately equal to the height that you desire. Polybutylene pipe for the trunnion (swivel) for the telescope tubing Diameter = 2", Length = approximately 2 pieces about 1" long This is glued to the tube bracket assembly with Wood glue Plastic furniture tacks These are used to stick into the bottom of the legs of chairs to protect the floor. They provide the foundation for the trunnions to turn. Wing Screws These are used for the end plates of the tube bracket assembly. They allow for the different telescopes to be used, just by unscrewing these and inserting a different telescope. Plastic floor flanges which can hold the big tubing and be nailed to the wood Nails, Bolts, Screws A whole lot of plywood! Suggested Tools: Power Saw circular saw Power Drill glue work bench to cut out various shapes of wood Instructions: The base is constructed by attaching the plastic holder to a square piece of plywood and then adding four legs which extend outward. The big plastic tubing can be glued into the holder. At the top of the tubing, another plastic holder is put on, but not glued, so that the entire top of the mounting can be removed for adjustments and travel purposes. The top plastic holder is attached to a round piece of plywood which has a whole cut out of the middle and a screw inserted there. The support box will be attached here and can swivel 360 degrees. The support box is constructed much like a shoe box except that one side is missing. The bottom has a rectangle cut out of end (see where Travis's hand is). This allows the bracket assembly to rotate all the way to a position perpendicular to the ground. Also, on the end of the box opposite Travis, cut out a semicircle to allow the telescope to rotate all the way to a position parallel to the ground. The bracket assembly encases the telescope. It looks like this: It is made up of a rectangular three-sided box with end plates on either end (bottom). The end plates (at the top) have wing screws which allow the top half of the end plate to be removed from the tube bracket assembly, releasing the telescope. This is useful for making adjustments to the telescope itself or for using a different powered telescope in the same mounting. Notice also the round wooden pieces attached to either side of the support box in the above picture. Wood glue is applied around the circumference of the circle and the smaller plastic tubes, only about an inch in length, are squeezed on. These are the trunnions. The unique part of the mounting is the trunnion. Trunnion notch plates are attached to the insides of the left and right walls (when looking through the telescope) of the support box. Plastic Furniture tacks are stuck into the insides of the triangular cut-out and support the trunnions. These tacks can be moved at any time to increase or decrease friction so that the trunnions will move smoothly, but also not allow the tube bracket assembly (and thus the telescope) to slip. The tube bracket assembly, telescope, and support box combined can be removed from the base. The result is that our telescope moves freely through an entire hemisphere giving us the ability to look at anything in the sky. It was with this mounting that we were finally able to recreate some of Galileo's observations. If you would like more information on how to build a relatively cheap mounting for your Galilean telescope, just e-mail Tom Williams or Jessica Williams. Return to the astronomy group's home page .

Increasing the magnification on the Galilean telescope, like all telescopes, reduces the field of view. Perhaps Galileo built a 30X telescope, but it is doubtful that he used much in his observations. The field of view must have been very tiny. How do you make a Galilean telescope?Building the Telescope Tube: Last Year's Group's Work Parts List (With approximate cost): Cardboard Telescoping Mailing Tube (1), $3 Diameter = 50mm (or 2"), Length = 1100mm (or 143") Should be comprised of an inner and outer tube with closed ends on the outer tube. Concave Convex Lens (the "objective lens") (1), $16 for this and the next lens as a pair. Focal Length = 1350mm (0.75 diopter) Cut to our specification of 49mm diameter. Plano Concave Lens (the "eyepiece") (1) Focal Length = -152mm (-6.6 diopter), Diameter = 49mm Cut to our specification of 49mm diameter. Suggested Tools: Coping Saw Alternatively, any other instrument that will make a relatively clean cut through the mailing tube. Drill (bit sizes discussed below) Super Glue Alternatively, any other kind of glue that will firmly hold the inner and outer mailing tubes together. It must be of a thin consistency. Greenlee Punch (optional) Instructions: The basic premise of the telescope tube is to align two lenses the appropriate distance from each other. For this telescope, the lenses are a concave convex (one side curved out and the other curved in) and a plano concave (one flat side and one side curved in). The plano concave lens is used as the "eyepiece" with the plano (flat) side facing the eye. The concave convex is used as the "objective lens" that is aligned with the eyepiece and with the convex side facing the sky. Notice that this lens is actually different than the plano convex lens used in the original Galilean telescope, but still gives the same results. The following design uses pieces of the inner tube of the mailing tube to hold the lenses in place inside the outer tube. This is best illustrated in the following diagram, which shows the cross section of the telescope tube: The outer tube of the mailing tube should have a short end that pulls off, and this can be used for the split in the outer tube shown above. This end will be used to hold the eyepiece. The inner tube must have two pieces (about 1" to 1.5" each) cut off of it that will be used as spacers to hold the objective lens in place. Make these cuts as straight and clean as possible, which will be difficult since the tube is made out of cardboard. A coping saw works pretty well for this. Take the short piece of the outer tube and cut or drill a hole (from 3/16" to 5/16" should be fine) directly in the center of the metal cap on the end. This will be the eyehole. It is important that this hole be as clean as possible (no metal protrusions) so that the the flat side of the eyepiece will fit snugly against the metal cap. An electrician's hole punch or Greenlee Punch works well for this task. If a drill is used, drill with a light pressure, then smooth out the inside surface as much as possible. Place the eyepiece flush (flat side) against the inside of this eyehole. The large piece of the inner mailing tube left will be used to hold this in place. To do this, drill small holes around the outside of the eyepiece tube. Then, with the eyepiece properly in place, slide the inner tube into it, put glue into the holes, and turn the tube a little bit to spread the glue inside. Hold the tube snugly against the lens inside the cap until the glue dries. Now, put this aside and take the large outer tube and the two spacers cut from the inner tube. Cut the closed end off of the outer tube, then use the other end to mount the objective lens (since that end already has a clean cut). Again, the "drill holes - put in glue" technique will be used to hold the spacers in place. First, check how far the inner spacer needs to be placed inside the tube so that the lens and other spacer will be able to sit inside the tube comfortably. Then drill holes in the outer tube around this area and glue in the spacer as before. After the first spacer is in place and dry, place the concave side of the objective lens flush against it, and put the other spacer snugly against the lens to hold it in place (again using the drill - glue method). Now there are two pieces, each containing one of the lenses. Slide the mailing tubes together as shown in the drawing above, and the telescope is done. By leaving these two pieces unglued, the telescope may be focused simply by sliding the eyepiece part inside the objective part. After a desired magnification/focus is found, the two pieces may be permanently attached (or some tape will give a semi-permanent attachment). Two images of a finished tube are shown below. The first picture shows the telescope tube from the objective side while the second image shows the ocular end of the tube: Making the Mounting: This Year's Work For the first half of the semester, we used the mountings built by last year's group. It looked like this: This image was produced by the star jumping in the field of view. We tried to have one person hold the telescope tube steady, but it takes very little movement to cause a star to move across the field of view when the field of view is only about 15 arc minutes. Moreover, our telescope would blow over often and required one person to hold it as still as possible, but this never really worked very well. So, we built a new mounting and stars looked like this, with very little distortion. The new mounting was constructed on a Saturday morning and afternoon, based on plans by Tom Williams. It looks like this: This telescope mounting is composed of a base a support box for the telescope tubing and its bracket assembly a bracket assembly encasing the telescope tubing with trunnion bearings which fit into the trunnion notch plates attached to the inside of the support box Parts List: Polybutylene Pipe Diameter = 4", Length = approximately 5' These can vary. The length is approximately equal to the height that you desire. Polybutylene pipe for the trunnion (swivel) for the telescope tubing Diameter = 2", Length = approximately 2 pieces about 1" long This is glued to the tube bracket assembly with Wood glue Plastic furniture tacks These are used to stick into the bottom of the legs of chairs to protect the floor. They provide the foundation for the trunnions to turn. Wing Screws These are used for the end plates of the tube bracket assembly. They allow for the different telescopes to be used, just by unscrewing these and inserting a different telescope. Plastic floor flanges which can hold the big tubing and be nailed to the wood Nails, Bolts, Screws A whole lot of plywood! Suggested Tools: Power Saw circular saw Power Drill glue work bench to cut out various shapes of wood Instructions: The base is constructed by attaching the plastic holder to a square piece of plywood and then adding four legs which extend outward. The big plastic tubing can be glued into the holder. At the top of the tubing, another plastic holder is put on, but not glued, so that the entire top of the mounting can be removed for adjustments and travel purposes. The top plastic holder is attached to a round piece of plywood which has a whole cut out of the middle and a screw inserted there. The support box will be attached here and can swivel 360 degrees. The support box is constructed much like a shoe box except that one side is missing. The bottom has a rectangle cut out of end (see where Travis's hand is). This allows the bracket assembly to rotate all the way to a position perpendicular to the ground. Also, on the end of the box opposite Travis, cut out a semicircle to allow the telescope to rotate all the way to a position parallel to the ground. The bracket assembly encases the telescope. It looks like this: It is made up of a rectangular three-sided box with end plates on either end (bottom). The end plates (at the top) have wing screws which allow the top half of the end plate to be removed from the tube bracket assembly, releasing the telescope. This is useful for making adjustments to the telescope itself or for using a different powered telescope in the same mounting. Notice also the round wooden pieces attached to either side of the support box in the above picture. Wood glue is applied around the circumference of the circle and the smaller plastic tubes, only about an inch in length, are squeezed on. These are the trunnions. The unique part of the mounting is the trunnion. Trunnion notch plates are attached to the insides of the left and right walls (when looking through the telescope) of the support box. Plastic Furniture tacks are stuck into the insides of the triangular cut-out and support the trunnions. These tacks can be moved at any time to increase or decrease friction so that the trunnions will move smoothly, but also not allow the tube bracket assembly (and thus the telescope) to slip. The tube bracket assembly, telescope, and support box combined can be removed from the base. The result is that our telescope moves freely through an entire hemisphere giving us the ability to look at anything in the sky. It was with this mounting that we were finally able to recreate some of Galileo's observations. If you would like more information on how to build a relatively cheap mounting for your Galilean telescope, just e-mail Tom Williams or Jessica Williams. Return to the astronomy group's home page .

Diffraction gratingsin physics

Two images of a finished tube are shown below. The first picture shows the telescope tube from the objective side while the second image shows the ocular end of the tube: Making the Mounting: This Year's Work For the first half of the semester, we used the mountings built by last year's group. It looked like this: This image was produced by the star jumping in the field of view. We tried to have one person hold the telescope tube steady, but it takes very little movement to cause a star to move across the field of view when the field of view is only about 15 arc minutes. Moreover, our telescope would blow over often and required one person to hold it as still as possible, but this never really worked very well. So, we built a new mounting and stars looked like this, with very little distortion. The new mounting was constructed on a Saturday morning and afternoon, based on plans by Tom Williams. It looks like this: This telescope mounting is composed of a base a support box for the telescope tubing and its bracket assembly a bracket assembly encasing the telescope tubing with trunnion bearings which fit into the trunnion notch plates attached to the inside of the support box Parts List: Polybutylene Pipe Diameter = 4", Length = approximately 5' These can vary. The length is approximately equal to the height that you desire. Polybutylene pipe for the trunnion (swivel) for the telescope tubing Diameter = 2", Length = approximately 2 pieces about 1" long This is glued to the tube bracket assembly with Wood glue Plastic furniture tacks These are used to stick into the bottom of the legs of chairs to protect the floor. They provide the foundation for the trunnions to turn. Wing Screws These are used for the end plates of the tube bracket assembly. They allow for the different telescopes to be used, just by unscrewing these and inserting a different telescope. Plastic floor flanges which can hold the big tubing and be nailed to the wood Nails, Bolts, Screws A whole lot of plywood! Suggested Tools: Power Saw circular saw Power Drill glue work bench to cut out various shapes of wood Instructions: The base is constructed by attaching the plastic holder to a square piece of plywood and then adding four legs which extend outward. The big plastic tubing can be glued into the holder. At the top of the tubing, another plastic holder is put on, but not glued, so that the entire top of the mounting can be removed for adjustments and travel purposes. The top plastic holder is attached to a round piece of plywood which has a whole cut out of the middle and a screw inserted there. The support box will be attached here and can swivel 360 degrees. The support box is constructed much like a shoe box except that one side is missing. The bottom has a rectangle cut out of end (see where Travis's hand is). This allows the bracket assembly to rotate all the way to a position perpendicular to the ground. Also, on the end of the box opposite Travis, cut out a semicircle to allow the telescope to rotate all the way to a position parallel to the ground. The bracket assembly encases the telescope. It looks like this: It is made up of a rectangular three-sided box with end plates on either end (bottom). The end plates (at the top) have wing screws which allow the top half of the end plate to be removed from the tube bracket assembly, releasing the telescope. This is useful for making adjustments to the telescope itself or for using a different powered telescope in the same mounting. Notice also the round wooden pieces attached to either side of the support box in the above picture. Wood glue is applied around the circumference of the circle and the smaller plastic tubes, only about an inch in length, are squeezed on. These are the trunnions. The unique part of the mounting is the trunnion. Trunnion notch plates are attached to the insides of the left and right walls (when looking through the telescope) of the support box. Plastic Furniture tacks are stuck into the insides of the triangular cut-out and support the trunnions. These tacks can be moved at any time to increase or decrease friction so that the trunnions will move smoothly, but also not allow the tube bracket assembly (and thus the telescope) to slip. The tube bracket assembly, telescope, and support box combined can be removed from the base. The result is that our telescope moves freely through an entire hemisphere giving us the ability to look at anything in the sky. It was with this mounting that we were finally able to recreate some of Galileo's observations. If you would like more information on how to build a relatively cheap mounting for your Galilean telescope, just e-mail Tom Williams or Jessica Williams. Return to the astronomy group's home page .

The bracket assembly encases the telescope. It looks like this: It is made up of a rectangular three-sided box with end plates on either end (bottom). The end plates (at the top) have wing screws which allow the top half of the end plate to be removed from the tube bracket assembly, releasing the telescope. This is useful for making adjustments to the telescope itself or for using a different powered telescope in the same mounting. Notice also the round wooden pieces attached to either side of the support box in the above picture. Wood glue is applied around the circumference of the circle and the smaller plastic tubes, only about an inch in length, are squeezed on. These are the trunnions. The unique part of the mounting is the trunnion. Trunnion notch plates are attached to the insides of the left and right walls (when looking through the telescope) of the support box. Plastic Furniture tacks are stuck into the insides of the triangular cut-out and support the trunnions. These tacks can be moved at any time to increase or decrease friction so that the trunnions will move smoothly, but also not allow the tube bracket assembly (and thus the telescope) to slip. The tube bracket assembly, telescope, and support box combined can be removed from the base. The result is that our telescope moves freely through an entire hemisphere giving us the ability to look at anything in the sky. It was with this mounting that we were finally able to recreate some of Galileo's observations. If you would like more information on how to build a relatively cheap mounting for your Galilean telescope, just e-mail Tom Williams or Jessica Williams. Return to the astronomy group's home page .

Suggested Tools: Power Saw circular saw Power Drill glue work bench to cut out various shapes of wood Instructions: The base is constructed by attaching the plastic holder to a square piece of plywood and then adding four legs which extend outward. The big plastic tubing can be glued into the holder. At the top of the tubing, another plastic holder is put on, but not glued, so that the entire top of the mounting can be removed for adjustments and travel purposes. The top plastic holder is attached to a round piece of plywood which has a whole cut out of the middle and a screw inserted there. The support box will be attached here and can swivel 360 degrees. The support box is constructed much like a shoe box except that one side is missing. The bottom has a rectangle cut out of end (see where Travis's hand is). This allows the bracket assembly to rotate all the way to a position perpendicular to the ground. Also, on the end of the box opposite Travis, cut out a semicircle to allow the telescope to rotate all the way to a position parallel to the ground. The bracket assembly encases the telescope. It looks like this: It is made up of a rectangular three-sided box with end plates on either end (bottom). The end plates (at the top) have wing screws which allow the top half of the end plate to be removed from the tube bracket assembly, releasing the telescope. This is useful for making adjustments to the telescope itself or for using a different powered telescope in the same mounting. Notice also the round wooden pieces attached to either side of the support box in the above picture. Wood glue is applied around the circumference of the circle and the smaller plastic tubes, only about an inch in length, are squeezed on. These are the trunnions. The unique part of the mounting is the trunnion. Trunnion notch plates are attached to the insides of the left and right walls (when looking through the telescope) of the support box. Plastic Furniture tacks are stuck into the insides of the triangular cut-out and support the trunnions. These tacks can be moved at any time to increase or decrease friction so that the trunnions will move smoothly, but also not allow the tube bracket assembly (and thus the telescope) to slip. The tube bracket assembly, telescope, and support box combined can be removed from the base. The result is that our telescope moves freely through an entire hemisphere giving us the ability to look at anything in the sky. It was with this mounting that we were finally able to recreate some of Galileo's observations. If you would like more information on how to build a relatively cheap mounting for your Galilean telescope, just e-mail Tom Williams or Jessica Williams. Return to the astronomy group's home page .

Take the short piece of the outer tube and cut or drill a hole (from 3/16" to 5/16" should be fine) directly in the center of the metal cap on the end. This will be the eyehole. It is important that this hole be as clean as possible (no metal protrusions) so that the the flat side of the eyepiece will fit snugly against the metal cap. An electrician's hole punch or Greenlee Punch works well for this task. If a drill is used, drill with a light pressure, then smooth out the inside surface as much as possible. Place the eyepiece flush (flat side) against the inside of this eyehole. The large piece of the inner mailing tube left will be used to hold this in place. To do this, drill small holes around the outside of the eyepiece tube. Then, with the eyepiece properly in place, slide the inner tube into it, put glue into the holes, and turn the tube a little bit to spread the glue inside. Hold the tube snugly against the lens inside the cap until the glue dries. Now, put this aside and take the large outer tube and the two spacers cut from the inner tube. Cut the closed end off of the outer tube, then use the other end to mount the objective lens (since that end already has a clean cut). Again, the "drill holes - put in glue" technique will be used to hold the spacers in place. First, check how far the inner spacer needs to be placed inside the tube so that the lens and other spacer will be able to sit inside the tube comfortably. Then drill holes in the outer tube around this area and glue in the spacer as before. After the first spacer is in place and dry, place the concave side of the objective lens flush against it, and put the other spacer snugly against the lens to hold it in place (again using the drill - glue method). Now there are two pieces, each containing one of the lenses. Slide the mailing tubes together as shown in the drawing above, and the telescope is done. By leaving these two pieces unglued, the telescope may be focused simply by sliding the eyepiece part inside the objective part. After a desired magnification/focus is found, the two pieces may be permanently attached (or some tape will give a semi-permanent attachment). Two images of a finished tube are shown below. The first picture shows the telescope tube from the objective side while the second image shows the ocular end of the tube: Making the Mounting: This Year's Work For the first half of the semester, we used the mountings built by last year's group. It looked like this: This image was produced by the star jumping in the field of view. We tried to have one person hold the telescope tube steady, but it takes very little movement to cause a star to move across the field of view when the field of view is only about 15 arc minutes. Moreover, our telescope would blow over often and required one person to hold it as still as possible, but this never really worked very well. So, we built a new mounting and stars looked like this, with very little distortion. The new mounting was constructed on a Saturday morning and afternoon, based on plans by Tom Williams. It looks like this: This telescope mounting is composed of a base a support box for the telescope tubing and its bracket assembly a bracket assembly encasing the telescope tubing with trunnion bearings which fit into the trunnion notch plates attached to the inside of the support box Parts List: Polybutylene Pipe Diameter = 4", Length = approximately 5' These can vary. The length is approximately equal to the height that you desire. Polybutylene pipe for the trunnion (swivel) for the telescope tubing Diameter = 2", Length = approximately 2 pieces about 1" long This is glued to the tube bracket assembly with Wood glue Plastic furniture tacks These are used to stick into the bottom of the legs of chairs to protect the floor. They provide the foundation for the trunnions to turn. Wing Screws These are used for the end plates of the tube bracket assembly. They allow for the different telescopes to be used, just by unscrewing these and inserting a different telescope. Plastic floor flanges which can hold the big tubing and be nailed to the wood Nails, Bolts, Screws A whole lot of plywood! Suggested Tools: Power Saw circular saw Power Drill glue work bench to cut out various shapes of wood Instructions: The base is constructed by attaching the plastic holder to a square piece of plywood and then adding four legs which extend outward. The big plastic tubing can be glued into the holder. At the top of the tubing, another plastic holder is put on, but not glued, so that the entire top of the mounting can be removed for adjustments and travel purposes. The top plastic holder is attached to a round piece of plywood which has a whole cut out of the middle and a screw inserted there. The support box will be attached here and can swivel 360 degrees. The support box is constructed much like a shoe box except that one side is missing. The bottom has a rectangle cut out of end (see where Travis's hand is). This allows the bracket assembly to rotate all the way to a position perpendicular to the ground. Also, on the end of the box opposite Travis, cut out a semicircle to allow the telescope to rotate all the way to a position parallel to the ground. The bracket assembly encases the telescope. It looks like this: It is made up of a rectangular three-sided box with end plates on either end (bottom). The end plates (at the top) have wing screws which allow the top half of the end plate to be removed from the tube bracket assembly, releasing the telescope. This is useful for making adjustments to the telescope itself or for using a different powered telescope in the same mounting. Notice also the round wooden pieces attached to either side of the support box in the above picture. Wood glue is applied around the circumference of the circle and the smaller plastic tubes, only about an inch in length, are squeezed on. These are the trunnions. The unique part of the mounting is the trunnion. Trunnion notch plates are attached to the insides of the left and right walls (when looking through the telescope) of the support box. Plastic Furniture tacks are stuck into the insides of the triangular cut-out and support the trunnions. These tacks can be moved at any time to increase or decrease friction so that the trunnions will move smoothly, but also not allow the tube bracket assembly (and thus the telescope) to slip. The tube bracket assembly, telescope, and support box combined can be removed from the base. The result is that our telescope moves freely through an entire hemisphere giving us the ability to look at anything in the sky. It was with this mounting that we were finally able to recreate some of Galileo's observations. If you would like more information on how to build a relatively cheap mounting for your Galilean telescope, just e-mail Tom Williams or Jessica Williams. Return to the astronomy group's home page .

Diffractiongrating experiment

The first diffraction grating was invented by Joseph von Fraunhofer in 1821. Fraunhofer, a German optician and physicist, used a metal plate with thousands of parallel lines to diffract light and produce a spectrum of light. This was a significant development in the study of diffraction and the development of spectroscopy, as it allowed scientists to analyze the spectral lines of various materials and study their properties.

Now there are two pieces, each containing one of the lenses. Slide the mailing tubes together as shown in the drawing above, and the telescope is done. By leaving these two pieces unglued, the telescope may be focused simply by sliding the eyepiece part inside the objective part. After a desired magnification/focus is found, the two pieces may be permanently attached (or some tape will give a semi-permanent attachment). Two images of a finished tube are shown below. The first picture shows the telescope tube from the objective side while the second image shows the ocular end of the tube: Making the Mounting: This Year's Work For the first half of the semester, we used the mountings built by last year's group. It looked like this: This image was produced by the star jumping in the field of view. We tried to have one person hold the telescope tube steady, but it takes very little movement to cause a star to move across the field of view when the field of view is only about 15 arc minutes. Moreover, our telescope would blow over often and required one person to hold it as still as possible, but this never really worked very well. So, we built a new mounting and stars looked like this, with very little distortion. The new mounting was constructed on a Saturday morning and afternoon, based on plans by Tom Williams. It looks like this: This telescope mounting is composed of a base a support box for the telescope tubing and its bracket assembly a bracket assembly encasing the telescope tubing with trunnion bearings which fit into the trunnion notch plates attached to the inside of the support box Parts List: Polybutylene Pipe Diameter = 4", Length = approximately 5' These can vary. The length is approximately equal to the height that you desire. Polybutylene pipe for the trunnion (swivel) for the telescope tubing Diameter = 2", Length = approximately 2 pieces about 1" long This is glued to the tube bracket assembly with Wood glue Plastic furniture tacks These are used to stick into the bottom of the legs of chairs to protect the floor. They provide the foundation for the trunnions to turn. Wing Screws These are used for the end plates of the tube bracket assembly. They allow for the different telescopes to be used, just by unscrewing these and inserting a different telescope. Plastic floor flanges which can hold the big tubing and be nailed to the wood Nails, Bolts, Screws A whole lot of plywood! Suggested Tools: Power Saw circular saw Power Drill glue work bench to cut out various shapes of wood Instructions: The base is constructed by attaching the plastic holder to a square piece of plywood and then adding four legs which extend outward. The big plastic tubing can be glued into the holder. At the top of the tubing, another plastic holder is put on, but not glued, so that the entire top of the mounting can be removed for adjustments and travel purposes. The top plastic holder is attached to a round piece of plywood which has a whole cut out of the middle and a screw inserted there. The support box will be attached here and can swivel 360 degrees. The support box is constructed much like a shoe box except that one side is missing. The bottom has a rectangle cut out of end (see where Travis's hand is). This allows the bracket assembly to rotate all the way to a position perpendicular to the ground. Also, on the end of the box opposite Travis, cut out a semicircle to allow the telescope to rotate all the way to a position parallel to the ground. The bracket assembly encases the telescope. It looks like this: It is made up of a rectangular three-sided box with end plates on either end (bottom). The end plates (at the top) have wing screws which allow the top half of the end plate to be removed from the tube bracket assembly, releasing the telescope. This is useful for making adjustments to the telescope itself or for using a different powered telescope in the same mounting. Notice also the round wooden pieces attached to either side of the support box in the above picture. Wood glue is applied around the circumference of the circle and the smaller plastic tubes, only about an inch in length, are squeezed on. These are the trunnions. The unique part of the mounting is the trunnion. Trunnion notch plates are attached to the insides of the left and right walls (when looking through the telescope) of the support box. Plastic Furniture tacks are stuck into the insides of the triangular cut-out and support the trunnions. These tacks can be moved at any time to increase or decrease friction so that the trunnions will move smoothly, but also not allow the tube bracket assembly (and thus the telescope) to slip. The tube bracket assembly, telescope, and support box combined can be removed from the base. The result is that our telescope moves freely through an entire hemisphere giving us the ability to look at anything in the sky. It was with this mounting that we were finally able to recreate some of Galileo's observations. If you would like more information on how to build a relatively cheap mounting for your Galilean telescope, just e-mail Tom Williams or Jessica Williams. Return to the astronomy group's home page .