Jump to content

  •  

CNers have asked about a donation box for Cloudy Nights over the years, so here you go. Donation is not required by any means, so please enjoy your stay.

Photo

Camera sensor size/telescope compatibility

  • Please log in to reply
8 replies to this topic

#1 michaelwriting

michaelwriting

    Lift Off

  • *****
  • topic starter
  • Posts: 10
  • Joined: 17 Nov 2018

Posted 19 November 2019 - 01:30 PM

I have been thinking about moving up from a Canon t6i to a 6D. I have seen comments saying that full frame sensors can potentially be too large for some telescopes, causing additional vignetting or cutoff at the corners.

 

How do you figure/calculate whether a camera sensor size and telescope are 'compatible'? I entered my equipment into astronomy.tools, but I'm not exactly sure what I should be looking for.

 

Thanks, Mike



#2 Nicole Sharp

Nicole Sharp

    Surveyor 1

  • -----
  • Posts: 1599
  • Joined: 12 Jun 2018
  • Loc: Cumberland, Maryland, USA

Posted 19 November 2019 - 01:38 PM

Whether or not the field of view in the camera sensor is vignetted is determined by whether the largest dimension of the camera sensor is larger or smaller than the smallest dimension in the telescope determining the field of view (the diameter of the image circle).  In a refractor, this is usually just the focuser diameter.  In an astrographic Newtonian, this is usually either the focuser diameter or the diameter of the secondary mirror (whichever is smaller).  In a Cassegrainian, this is usually either the focuser diameter, the diameter of the secondary mirror, or the diameter of the baffle tube (whichever is smallest).  A full-frame camera (sensor size of 36*24 mm^2 with a diagonal of 43 mm) will always be vignetted in a 32-mm (1.25-inch) focuser, since (43 mm > 32 mm).

 

A visual test to check the field of view would be to try to use an eyepiece with a focal length of 43 mm (roughly equivalent to the field of view in a 43-mm camera sensor).  I don't think anyone makes a 43-mm eyepiece, but a 42-mm eyepiece should be close.  Note that they are not available in 1.25-inch barrel sizes, since a 42-mm eyepiece would be vignetted in a 32-mm focuser (same as a full-frame camera sensor would be).


Edited by Nicole Sharp, 19 November 2019 - 01:52 PM.

  • B 26354 likes this

#3 Jim Waters

Jim Waters

    Gemini

  • *****
  • Posts: 3193
  • Joined: 21 Oct 2007
  • Loc: Phoenix, AZ USA

Posted 19 November 2019 - 02:07 PM

I have a Canon 6D and I get 'moderate' vignetting on my Stellarvue 90mm f/7 w/ 2.5" focuser with a 0.8x FR/FF.  I get some vignetting at f/7.

 

I got 'significant' vignetting on my 8" f/4 Newt to the point where images were not usable....

 

If I had to do it again I would get an APS-C camera.


  • bmhjr likes this

#4 photoracer18

photoracer18

    Mercury-Atlas

  • *****
  • Posts: 2976
  • Joined: 02 Sep 2013
  • Loc: Martinsburg, WV

Posted 19 November 2019 - 02:27 PM

Stick with APS-C in my opinion. Even though I have a full frame digital in my regular camera gear I have never been tempted to try it since I have 2 astro-modded APS-C plus a couple of dedicated astro cameras. If I wanted to go wide field I would just use a camera lens instead of a telescope. Even using a focal reducer I can't get any of my current telescopes to go shorter than some of my best camera lenses.


Edited by photoracer18, 19 November 2019 - 02:28 PM.

  • Jim Waters likes this

#5 bobzeq25

bobzeq25

    Hubble

  • *****
  • Posts: 17373
  • Joined: 27 Oct 2014

Posted 19 November 2019 - 02:31 PM

I have been thinking about moving up from a Canon t6i to a 6D. I have seen comments saying that full frame sensors can potentially be too large for some telescopes, causing additional vignetting or cutoff at the corners.

 

How do you figure/calculate whether a camera sensor size and telescope are 'compatible'? I entered my equipment into astronomy.tools, but I'm not exactly sure what I should be looking for.

 

Thanks, Mike

You get the manufacturers specification for image circle.

 

But, in general, most scopes will have substantial vignetting and or aberrations at the corners that make stars look funny.  If a scope is compatible with a full frame camera the manufacturer will generally advertise that.  And the scope will generally be priced accordingly (high).


  • Jim Waters, MikeMiller and bmhjr like this

#6 scadvice

scadvice

    Surveyor 1

  • *****
  • Vendors
  • Posts: 1552
  • Joined: 20 Feb 2018
  • Loc: Lodi, California

Posted 19 November 2019 - 02:45 PM

Try using Astronomy tools to get an idea.

 

https://astronomy.to.../field_of_view/



#7 bmhjr

bmhjr

    Apollo

  • ****-
  • Posts: 1299
  • Joined: 02 Oct 2015
  • Loc: Colorado

Posted 19 November 2019 - 02:49 PM

I agree to all of above.  Even with very little vignetting you could have misshapen stars at the edges from a not flat field.  With my Stellarvue 80mm f6 and 2.5 inch focuser, I see very little to no vignetting with my full frame camera.  But the stars in the corners are wonky.  


  • Jim Waters and MikeMiller like this

#8 MikeMiller

MikeMiller

    Viking 1

  • -----
  • Posts: 736
  • Joined: 22 Jul 2014
  • Loc: Pittsburgh, PA, USA

Posted 19 November 2019 - 04:09 PM

You also need to be aware of any reducers, flatteners, filters, and other adapters. Even if the scope supports FF, it is only as wide as it's narrowest chokepoint. And, you may get vignetting no matter what, it just depends on what degree; and what degree of vignetting you can put up with. 

 

Many scopes made with imaging in mind will say what maximum imaging circle (sensor size) they are made to work with. Though I have found that a lot will be vague if it is anything less than full frame. Often it is the more expensive astrographs that support the larger image circles. If a scope supports full frame, that will almost certainly be listed in the marketing.

 

All of the (newer) William Optics scopes and flatteners that I have will image at full frame. 

The EdgeHD 8 is supposed to cover a FF circle, but the reducer is only designed for APS-C.

(I have not tested any of these personally, as all of my cameras are smaller than APS-C.)

 

The Orion 8" f/3.9 you have in your signature says less than 10% vignetting on APS-C, which is good, but doesn't mention FF at all. I think you can assume that there will be significant vignetting.

https://www.telescop...1450.uts#tabs-2

 

The ES ED102 doesn't say either way. 

https://explorescien...actor-telescope

 

If you have a scope/camera combination in mind, you could try to find other people using it on Astrobin.


Edited by MikeMiller, 19 November 2019 - 04:12 PM.


#9 Jeffmar

Jeffmar

    Viking 1

  • -----
  • Posts: 741
  • Joined: 18 Mar 2012
  • Loc: salt lake city, utah

Posted 20 November 2019 - 05:54 PM

I have recently been using full frame cameras. I also have been getting more vignetting. That is the down side. The up side is the significantly better dynamic range and decreased noise. For dim DSO’s I take 2 or 3 second exposures at 25000 to 50000 ISO to help me center the target and get a good focus. The interesting thing is some of those photos aren’t half bad. Longer exposures at lower ISO’s are certainly cleaner but I find with any of my cameras. I can do 20 second exposures at 10,000 ISO and still get usable photos to stack and process. That is something I couldn’t do with my aps-c cameras. I lost way too much detail and got way too much noise at anything above 3200 ISO with the smaller sensors. 

 

Cmos sensors are getting more sensitive and produce cleaner images especially with some of the processing dslr and mirrorless cameras have. 

 

I have only been using my Sony full frame cameras for astrophotos for about 4 months but have been very pleasantly surprised at how good they are on the end of a telescope. I just put up with some vignetting and crop in enough to make a decent looking photo. I have also learned that a 1.25 inch adapter is not the way to go with even my aps-c cameras.


Edited by Jeffmar, 20 November 2019 - 08:43 PM.



CNers have asked about a donation box for Cloudy Nights over the years, so here you go. Donation is not required by any means, so please enjoy your stay.


Recent Topics






Cloudy Nights LLC
Cloudy Nights Sponsor: Astronomics