Telescope focalratio

The Optical Coherence Tomography (OCT) is a new medical imaging device. It uses ultrasound with light and enables user to visualize small structures and layers inside the tissue with a resolution of about 10 µm.

The last item I’ll mention is that you are able to change the focal length of your telescope through the use of focal extenders or focal reducers to adjust / improve the characteristics of your telescope which in turn will affect the F-ratio.

Focal lengthoftelescopeformula

This content is intended for health care professionals and providers only. The information contained on Beye.com, including text, graphics, images, and interactive activities, is for informational purposes only, and is not intended to be a substitute for professional medical advice. Beye LLC, via its Editors and Publisher, accepts no responsibility for any injury or damage to persons or property occasioned through the implementation of any ideas or use of any product described herein. Although great care is taken to ensure that all information is accurate, it is recommended that readers seek independent verification of advice on drugs and other product usage, surgical techniques and clinical processes prior to their use. References made in article may indicate usage of medical equipment or drugs at dosages, for periods of time, and in combination not included in the current prescribing information. Inclusion of advertising materials on the website thereof, does not constitute and representation or guarantee by Beye LLC of the quality of such products, or of the claims made.

Focal length telescopefor astrophotography

This content is intended for health care professionals and providers only. The information contained on Beye.com, including text, graphics, images, and interactive activities, is for informational purposes only, and is not intended to be a substitute for professional medical advice. Beye LLC, via its Editors and Publisher, accepts no responsibility for any injury or damage to persons or property occasioned through the implementation of any ideas or use of any product described herein. Although great care is taken to ensure that all information is accurate, it is recommended that readers seek independent verification of advice on drugs and other product usage, surgical techniques and clinical processes prior to their use. References made in article may indicate usage of medical equipment or drugs at dosages, for periods of time, and in combination not included in the current prescribing information. Inclusion of advertising materials on the website thereof, does not constitute and representation or guarantee by Beye LLC of the quality of such products, or of the claims made.

2000mmfocal length telescope

So, what does this mean for us astro photographers?  Faster F-ratio telescopes will allow you to collect more light in less time.  The consequences of this is that you will be able to get a lot of data by taking shorter sub exposures with a faster F-ratio.  Since you don’t need to take longer sub exposures, the imaging run will be less demanding on your mount and your auto guiding system.

Focal length telescopecalculator

To illustrate this, I have 2 telescopes I regularly image with using the same camera; one telescope is an Orion 8 inch (203 mm) newtonian astro graph that has a focal ratio of f/3.9.  The other telescope is an Astro Tech AT125 EDL (125 mm aperture) that has a focal ratio of f/6.95.  The Orion 8 inch newtonian astro graph is 3.2 times faster than the refractor.  So, the data I can get using 60 second exposures on the Orion telescope will require 192 seconds on the Astro Tech refractor to collect the same data.  In this case, I can get 3 exposures on the Orion (60 per hour of imaging) for every single exposure on the Astro Tech refractor (~19 per hour of imaging).

One of the major characteristics we look for when buying a telescope to use for imaging is what the F-ratio of the telescope is.  The best and most comprehensive treatment of this topic is from the Sky Watcher Webcast, “Understanding F Ratio” (that I encourage anyone struggling with this topic to watch.  What follows is a brief summary of that talk.

M109 (https://app.telescope.live/click-grab/all?target=m109 ); Telescope Live 1-Click Observation Data, Processed using PixInsight by Reggie Jones

F ratio is usually indicated with a designation and number such as f/3.9.  Simply put, this is an indication of the light gathering ability and the speed of the telescope.  The smaller the F-ratio, the more light gathering ability the telescope has or the faster the optic is and the brighter the target image will be for a specific exposure time.  The larger the F-ratio, the less light gathering ability it has or the slower the optic is and the dimmer the target image will be for the same specific exposure time.