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.


Full frame camera + 2" focuser - opinions?

  • Please log in to reply
3 replies to this topic

#1 JamesAL


    Lift Off

  • -----
  • topic starter
  • Posts: 1
  • Joined: 23 Jun 2021

Posted 24 June 2021 - 09:06 AM

So....my first post after creating an account but reading on and off for a long time!


Quick background - I just sold my ETX90 that I bought used; optically it was in great shape but there were bits and pieces missing that were annoying, and cost to add stuff on their own would exceed the cost of buying new. I took some really nice photos out of the top port with my Canon 60D (cropped sensor). I have a few Baader Hyperion eyepieces (13, 17, 21) and adapters to connect to an M42 mount. I also have my late 1980's Meade 226...put on some tube rings and bar and dropped it onto my Twilight 1 mount...and photos even with the .965 focuser are amazing!


I'm also into photography and have a 60D, and lots of lenses. I'm intending to buy the next R-series camera that will replace the RP unless I can get the RP at a steal of a deal price (R-series are full frame)


What I want to do - option 1

Looking to buy a Skywatcher Skymax 102 and do lots of moon photos out the back port. I'd like to have the full moon in view same as the ETX90).

But....it's sold out everywhere...


What I want to do - option 2

Buy a Skymax 127 - but I don't think I can get the full moon in view. This telescope had a 2" focuser though.

My main question - Has anyone used a full frame camera with a 2" M42 or M48 camera adapter with a Skymax, and can you get the whole moon in the full camera frame?


If I eventually get the full frame Canon RP I might as well build up the equipment for it now.


I'd like to stay with a Skymax if I can, as well as buy locally (Toronto area).


Oh ya...no I don't want a Dob, I don't have space for it, and it's too hard/noisy to set up when the kids are asleep smile.gif Needed to get that out there!





Edited by JamesAL, 24 June 2021 - 09:41 AM.

#2 meansrt


    Mariner 2

  • *****
  • Posts: 281
  • Joined: 05 May 2020

Posted 24 June 2021 - 09:47 AM

Download the program Stellarium and enter the stats on the telescope (focal length) and the Camera (sensor size and pixel count). You can use it to tell you exactly how big the moon would be in the camera FOV and not only the moon but any sky object. I just checked the EOS R with a 1600 mm focal length and the moon does fit so I'm sure it will fit even better in the two options youve listed. 

Edited by meansrt, 24 June 2021 - 09:50 AM.

#3 AgilityGuy


    Viking 1

  • -----
  • Posts: 849
  • Joined: 20 Jun 2015
  • Loc: Northern CA

Posted 24 June 2021 - 10:09 AM

I initially started imaging using a Nikon D7200 with an APS-C sized sensor and a Televue 85 with 2" focuser.  There was a moderate amount of vignetting with that setup but it did calibrate out fairly well with flats.  I haven't even tried my full frame Nikon on that telescope just for the reason I know there's going to be more vignetting than I want.  That said, the only way you'll know if the amount is acceptable and calibrate out is to give it a try.

#4 KLWalsh



  • -----
  • Posts: 1,020
  • Joined: 19 Feb 2014
  • Loc: North Georgia, USA

Posted 24 June 2021 - 12:43 PM

The Moon subtends an angle of about 1/2 of a degree.
The tangent of 0.5 degrees is about 0.00873.
The dimensions of a full frame sensor are approx. 24 x 36 mm.
If you divide 24 mm by 0.00873 you get 2750 mm.
If the focal length of your telescope is less than 2750 mm, the entire moon will fit on your sensor.

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