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It says a 'cheshire collimater' used for the primary mirror (so no lazers at all here then). Not knowing precisely what such a gizmo is, I wonder if anyone can suggest even a 1/2 decent way to collimate the primary w'out the realtive added expense of a cheshire or a lazer gizmo? (perhaps therefore good enough for the humble 'budget' 1st scope type 130EQ. Im sure it doesnt warrant the most precise collimater as a costly beastie would after all).

Hi there, Im new to the game and have the same 130EQ. I collimated the secondary mirror without a lazer which I have a hunch might be 'good enough' for our humble scopes (I may be wrong and a precise collimation of primary mirror 1 with lazer gizmo is essential too, but I think with care this might be ok).

A collimator is a device, often a piece of plastic with hole in the center of it and crosshairs to help collimate the telescope. Other collimators use a precision laser that is put into the focuser and then shines a laser at the secondary mirror, then at the primary mirror and back. The goal is to get the laser that has bounced back centered with the collimator itself, which usually has a bullseye type marking on it. Collimating is essential for optimum telescope performance, both for visual and astrophotography. Here's a collimator from Orion.

Lens manufacturers aim to provide circular apertures and use iris diaphragm blades with curved edges for this purpose. But even with curved blades, the circular bokeh effect appears only at wide apertures. The best way to ensure a smooth circular bokeh effect, even at narrow apertures, is to increase the number of blades (e.g., 11, 12, and 15). The result is a high-quality lens with less chromatic aberrations but more expensive.

It's not as complicated as it looks. Enjoy your scope and pick away at the collimation until it's good. It'll all come together in the end. You'll get reasonable views of most objects even if it's misaligned.

Get a film cannister cut the btm 1" off and put a precise pin hole in centre, pop in EP tube (make sure fit perfect 1st/ no droppings thru!). Then with OTA flat, & twd a light area, put a primary mirror cardboard 'stopper' (a bit of card bent into a T to gently put in to block mirror1) and a blue bit of card/ red whatever behind/ below mirror 2 for a blue even background (ie not black). Check:

What isirisin camera

However, you don’t have to compute the diameter or surface of the iris diaphragm’s aperture to know how much light you let pass through the lens. Lens manufacturers thought about it and decided to use an f-stop scale that halves the amount of light at each step. Using the powers of the square root of 2, they offer an f-stop scale looking like this: f/1.4, f/2, f/2.8, f/4, f/5.6, f/8, f/11, f/16, f/22. With each step up from f/1.4 towards f/22, you halve the amount of light that enters the lens.

A collimator is simply a tool to check the alignment of all the bits, and if they are not accurate then the best collimation cannot be achieved. A laser collimator needs to be checked that the laser is itself centered. Fairly easy but a necessity. Seems to be 2 main types:- Laser and Cheshire. There are I suspect others, think FLO have a Catseye unit that operate differently.

The iris diaphragm also impacts the brightness of what you see through the optical viewfinder, the apparition of the vignetting effect or chromatic aberration, the sharpness and contrast of the image, and even color saturation.

Others will be able to inform you a lot better than a simpleton-frac user I am, but for now, I think you'll find this guide a great read and help.

2) mirror2 is a perfect o and not a 0 for eg, ie aligned- if a slight 'rugby ball' then mirror2 needs a tweak around, where it is).

The iris diaphragm also influences the depth of field, allowing you to have more or less of the scenery in focus. Wide apertures produce a shallower depth of field, blurring the background and keeping just a small area in focus. Narrow apertures, on the other hand, produce a deeper depth of field, keeping more of the frame in focus.

1) mirror2 is perfectly central to the EP tube (if off LH ar RH the centre screw needs a tweak, ie move mirror2 in a fraction in or out).

Irislens camera

The f-stop scale is written on the lens (at least older ones), and a small dot sometimes marks the current selection. The maximum aperture of a lens is often included in the lens’ name (e.g., ZEISS Biogon T* 2.8/25 ZM). Some advanced lenses provide 1/3 f-stop intervals for increased aperture precision, and they mark the full stop positions to make it easier for you to comprehend the scale.

What collimation achieves is simple. Think of your telescope like the lens of an SLR camera. At the focal plane of the SLR lens there's the film or CCD chip. Imagine what would happen if the focal plan and CCD weren't parallel with eachother: you would never be able to focus properly. It's the same thing with your telescope. You align the optics in order to ensure that the focal plane of your eyepiece is coincident with the focal plane of the telescope objective. Here's some reading: http://www.physiol.ox.ac.uk/~raac/collimationLinks.shtml

A question not asked enough by observers (especially those with fast newts) is "Does my scope need any collimation adjustments?" And the answer is simple - do a star test that takes only a few seconds. No scope can be perfectly collimated but doing a star test will tell if you are as near to a perfect collimation as is practical. How often should my scope be adjusted? a simple star test will give you the answer every time you go out to observe.

Iriscontrol in camera

The "problem", if that is the correct term, is that optical settings need to be fairly accurate, when a beam is reflected any error is doubled. There are 2 mirrors in the path of a newtonian.

To open the iris diaphragm, you need an f-stop with a small number. If you want to close the iris diaphragm, you need an f-stop with a large number. For example, the diameter of the iris diaphragm’s aperture for a 50mm lens at f/1.4 is 35.7mm. At f/2, the diameter of the iris diaphragm’s aperture is 25mm. At f/22, the diameter of the iris diaphragm’s aperture is 2.27mm.

The bokeh effect is based on an optical phenomenon called the circle of confusion. In short, the circle of confusion means that the points of light in blurred areas resemble the iris diaphragm’s aperture. Hence, instead of being seen as regular points, they become heptagons or other polygonal shapes. However, the most popular and appreciated bokeh effect has circular shapes.

3) removed the cards, and checked that the 3 retaining clipss (look like small black clips against the primary mirror background now) are equally spaced, if one off or not same the its corresponding allen bolt needs a tweak 9you'll figure out which).

Back to an earlier point if the eyepiece cannot be held perpendicular to the main tube then you have a problem, as other then taking it off and putting it back on correctly they is nothing that can be done.

collimation is akin to tuning a guitar. you can still use a guitar and broadly get a tune out of it if not in tune but it will not perform as well as if it were properly adjusted. continuing the analogy, the more often you tune your guitar, the easier and quicker it gets.

Assuming it is then the secondary has to be positioned at 45 degrees to the eyepiece optical path and such that the centre of the secondary is also on the optical axis.

I bought my astromaster 130 and was to think it was set up and ready to point it up. Oh no iv gone and done some reading ( i know stupid me) and i have heard if collimators. what does it do?

The optimal setup for a beautiful bokeh effect requires a high-quality telephoto lens with many iris diaphragm blades and a wide maximum aperture and scenery with points of light far behind the focal plane.

When you adjust the aperture of a lens, a mechanism operates the iris diaphragm blades, making the opening wider or narrower. As a result, more or less light enters the camera, reaching the sensor and producing a brighter or darker image.

Collimation in terms of a reflector is setting the mirrors and eyepiece all in line and setting the secondary at the correct angle.

in telescope terms, collimation is just the proper alignment of the mirrors and other components to ensure they perform well. it's a simple process once you 'get it' and now takes me about a minute max. it's often a case of checking it and not doing anything as nothing is out of alignment.

The iris diaphragm controls how much light enters the camera and is essential for creating a well-exposed photo. By adjusting the size of the opening, one can let more or less light reach the sensor and thus create a brighter or darker image. Having an iris diaphragm with a wide aperture may help you take photos in low-lighting conditions without having to slow down the shutter speed or increase the ISO value too much.  As a result, you avoid camera shake blur and ISO noise.

You can only change the aperture in predetermined steps. You can’t close the iris diaphragm completely because no light will reach the sensor, and the camera won’t be able to take a photo. And you can’t open the iris diaphragm blades more than is physically possible by construction.

A "good" scope could very easily be one where the assembled items are checked and set up better. If the main mirror is checked to be central, and tweeked so it is perpendicular, if the secondary is attached so it is at 45 degrees and central and not just close enough, if the focuser is seated so that it is more accurate then that scope will perform better. Nothing there other then a little extra attention.

However, what is called aperture in photography is not the same as the aperture of the iris diaphragm. The concepts are connected but represent different things and have different measurement units. The lens’ aperture represents how much light gets through the lens at a given focal length and is measured in f-stops (or f-numbers). The aperture of the iris diaphragm is the physical opening in the diaphragm (aka effective aperture), and its diameter is measured in millimeters.

Having set these 2 correct then the main mirror has to be both centered and perpendicular to the optical axis, they tend to put a small marker on the mirror to aid in this. You adjust the main mirror to get this accomplished. If the main mirror is not perpendicular to the optical axis then you get coma - little egg shaped stars.

Iris apertureexplained

A iris diaphragm is a circular opaque device with one or more circular openings that let the light go through. The iris diaphragm is a diaphragm made of overlapping blades, with one central hole and the ability to change the diameter of the opening. It’s the type of diaphragm that resembles the human eye, which has the iris in the role of the diaphragm and the pupil in the role of the opening. The opening in the diaphragm is called the aperture. But, as we’ll see, it’s not the aperture we refer to in photography.

Therefore, the key to using f-stops is to remember that a full stop means doubling or halving the amount of light entering the lens. Similarly, shutter speeds double or halve with each step (e.g., 1/125, 1/250, 1/500, etc.). A twice faster shutter speed halves the amount of light entering the lens, while a twice slower shutter speed doubles it. Thus, if you want to increase the shutter speed with a certain number of steps and maintain the exposure, you need to set a wider aperture using the same number of steps.

Iris aperturemechanism

The iris diaphragm is in the lens, behind the front element. Therefore, it is part of the lens and not of the camera body, even if we adjust it from the camera.

Take a lens, tilt it around in front of your eye, and you'll see that the best view is when it's exactly square to your eye. The same applies to the reflection in a curved mirror. Collimation just means ensuring that the components are properly squared or aligned. The effect of not being properly aligned is in most cases very small and to a beginner probably not noticeable at all. So the advice to any beginner is not to start by worrying about collimation, but start by looking at stuff.

The thing about collimation is that you can check it and worry about it on cloudy nights or in the daytime, using tools that are in some cases quite expensive. This can make it a fatally attractive subject for people who don't get enough dark time.

Camerairisvsaperture

Small scopes hold their collimation very well and the factory setting is most likely fine, or at any rate good enough for enjoyable views. If you don't enjoy the views then the first things to think about are light pollution, using excessively high magnification, and various other faults. Eliminate those before worrying about collimation.

Bokeh is an effect that changes the quality of the blur. Under certain conditions, the points of light in the blurred area spread out, soften, and get an almost round shape. The effect is pleasing to the human eye, producing a calming, reverie-like feeling. The conditions for getting a nice bokeh effect include a shallow depth of field, small light sources or highlights in the out-of-focus area, and a high-quality iris diaphragm.

There is nothing requiring vast knowledge and experience or an optical test bench. An understanding of what you are aiming at accomplishing is useful otherwise you are going through a set of actions without knowing why and that means things do not get performed correctly.

Cameraaperture

The opening’s diameter is adjusted by controlling the overlapping of the diaphragm’s blades. Hence, the opening of an iris diaphragm is never perfectly circular, even if manufacturers aim to make it as circular as possible. For example, the AF Nikkor 50mm f/1.4D lens has seven diaphragm blades, and its aperture’s shape is a heptagon.

So, to adjust the iris diaphragm and allow more or less light to pass through the lens, you need to adjust the lens’ aperture, moving one step at a time. The steps are called f-stops and are represented by an f followed by a slash and number (e.g., f/2). For most lenses, f-stops range between f/1.4 and f/22.

Depth of field is also influenced by the focal length of the lens and the camera-subject distance. But if you aim for a shallow depth of field and a bokeh effect, the construction of the iris diaphragm is the one that dictates the quality of the effect.

Aperturein theiriscrossword clue

We often talk about aperture, shutter speed, and ISO because one can’t use the same camera settings for all their photos. Sometimes, we know that a particular set of parameters works best for a certain photographic genre. But these are just pointers, not the absolute truth. We still have to adapt camera settings to the real-life conditions in our photo setup, go through a try-and-error process, and improvise along the way. And while most of us heard about the aperture, few photographers know what the iris diaphragm is and how it influences their photos.

From what I understand, collimation is necessary for all scopes, even fracs, but due to their design, newts and cassegrains need a tad more care and attention. From this, I've wrongly or rightly concluded that collimation in the latter type scopes is an absolute necessary and must be done on a regular basis - how often I'm not sure, but I guess if you treat your scope well, not that often.

The iris diaphragm is an essential part of a lens with implications in exposure, composition, and overall photo quality. It is the mechanism behind the lens’ aperture and f-stops. And as you’ve seen, it influences the brightness of the photo, depth of field, bokeh effect, and other aspects.

If you find your high-power views look blurry, or galaxies look way too dim, or you just can't find what you're looking for, it's got nothing to do with collimation. If you find that out-of-focus stars in the centre of the field of view aren't circular then it might be a collimation issue.

The link below includes how to do such a test as well as lots of other info on the subject. As for collimating equipment, you don't need any to get very good results. Most times the primary mirror only may need adjustment during a star test.

If your telescope is out of collimation then the views will be blurry. There can be a vast difference in planetary views. Your telescope is f/5, which is a fairly fast focal ratio. Telescopes with faster focal ratios need more careful collimation.

Understanding how the iris diaphragm works helps you make an informed decision when purchasing a lens, use the aperture both as a technical and creative parameter, and produce high-quality unique photographs. Try to master the optics, mechanics, and math behind a camera because they provide a more reliable path for learning, and use the camera to your advantage without memorizing camera settings and parameters.