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Field of veiw of camera sensor?

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#1 scottk

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Posted 02 November 2013 - 09:00 PM

I have an AT6IN. Which is a 6" f/4 newtonian at 610mm fl.

The widest fov eyepiece I have is a orion 25mm plossl. Is the fov I get with that eyepiece wider or narrower than what I would get in an image with a aps-c sensor (canon t3i)?

#2 jrcrilly

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Posted 02 November 2013 - 10:05 PM

Here's how to obtain a rough approximation of FOV. It's rough because many of the parameters are known only approximately.

A 25m eyepiece in a 610mm telescope provides a magnification of about 610/25, or about 24X.

The Plossl has an apparent FOV of about 50 degrees. 50 degrees is 50X60 arcminutes, or 3000 arcminutes.

3000 divided by 24 gives about 125 arcminutes FOV.

An APS size sensor provides about 85 by 125 arcminutes at 610mm so that will be a little smaller than your eyepiece's true FOV..

#3 D_talley

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Posted 02 November 2013 - 10:18 PM

What I do is use this site to see a visual indication of what the field of view is. Your scope is not listed but you can put in the numbers and then plug in your eyepiece or camera to see what an example object will be. Also it will give you the actual field of view.

Field of view.

#4 scottk

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Posted 02 November 2013 - 10:43 PM

Wow! Thanks guys. Great help.

#5 WarmWeatherGuy

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Posted 03 November 2013 - 12:23 AM

I have an AT6IN. Which is a 6" f/4 newtonian at 610mm fl.

The widest fov eyepiece I have is a orion 25mm plossl. Is the fov I get with that eyepiece wider or narrower than what I would get in an image with a aps-c sensor (canon t3i)?


Your field of view is the chip size divided by 610mm (for the camera) or the size of the light hole of your eyepiece divided by 610mm (for the eyepiece). Look at the rear of your eyepiece to see the light hole. The answer is in radians. Multiply by 57.3 to convert to degrees.

If your chip is 23.6mm X 15.7mm then your field of view will be 2.2° X 1.5°.

If the light hole in the back of your eyepiece is 20mm then your field of view is 1.9°

Your apparent fov is your true fov times the power of the telescope.

#6 epdreher

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Posted 03 November 2013 - 01:16 AM

Steve, thanks for this info. I've looked for a simple formula, and this fits the bill.

#7 CounterWeight

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Posted 03 November 2013 - 11:04 AM

Dwight that is a great site, thanks for posting it - just added to my bookmarks.

In many of the planetarium software that allow for inputting your equipment you can use fov reticles created and selected in the software. I don't know how Stellarium does it, but SkyTool3pro and TheSky both have very capable tools for it.






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