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

Using a Diagonal

  • Please log in to reply
3 replies to this topic

#1 donsinger

donsinger

    Explorer 1

  • -----
  • topic starter
  • Posts: 82
  • Joined: 18 Dec 2018
  • Loc: Portland, OR

Posted 25 October 2020 - 11:26 PM

I just finished my first EAA session using a C6 on an Evolution mount, .63FR and an ASI294MC (not Pro) camera. I found that clearance is a problem (I have 105mm backfocus which works great) with viewing objects more than 55-60 degrees in elevation.

 

I understand that using an equatorial mount would be best, but my AVX and ASI533MC Pro are usually busy imaging on those few nights here in the Pacific NW that we have clear skies this time of year. It would be great if I could use the C6/EVO combination as my AVX is busy imaging.

 

I was wondering if I could effectively use a 2" diagonal with my EVO/294/FR combination, which would give me the clearance I need. Are there any downsides and, most importantly, I was wondering how much back focus the 2" diagonal adds to the image train (need to get t 105mm). I have searched the EAA forum but could not find the information I need.

 

Thanks in advance.

 

Don


Edited by donsinger, 25 October 2020 - 11:28 PM.


#2 GazingOli

GazingOli

    Ranger 4

  • -----
  • Posts: 303
  • Joined: 13 Oct 2019
  • Loc: Stuttgart GERMANY

Posted 25 October 2020 - 11:59 PM

Hello Don,

 

the Baader 2" standard diagonal adds 112 mm to your optica path, that is about what all 2" diagonals do. Baader might be a little more because of the Clicklock.

 

https://www.baader-p...nal-mirror.html

 

But Baader has a great variety of diagonals without barrel or Clicklock where you can get it shorter.

 

https://www.baader-p...-diagonals.html

 

Usually you can find the optical lengh in the technical data sheet of a diagonal (website of the manufacturer or manual).

 

CS.Oli


Edited by GazingOli, 26 October 2020 - 03:25 AM.


#3 Noah4x4

Noah4x4

    Soyuz

  • *****
  • Posts: 3,922
  • Joined: 07 Apr 2016
  • Loc: Colchester UK

Posted 26 October 2020 - 02:03 AM

I regularly use an Atik Horizon on Hyperstar on my Evolution 8" but occasionally want to Image at f/6.3 behind a focal reducer. Any cooled camera is too long and rear end clearance is a problem as you describe.

 

However, I deliberately bought the non-cooled ASI294mc (like you) and I can (just) achieve clearance by pushing my OTA fully forward. You should be able to do this with an even smaller 6" but many folk are obsessed with balancing their OTA. This is unnecessary with a notably robust Evolution and I find front end loading mine seems to assist with tracking and backlash.  The Evolution motor is powerful and its metal gears precise.


  • Broglock likes this

#4 donsinger

donsinger

    Explorer 1

  • -----
  • topic starter
  • Posts: 82
  • Joined: 18 Dec 2018
  • Loc: Portland, OR

Posted 26 October 2020 - 11:26 AM

Noah and Gs.oli thanks for the responses.

 

Noah, I had to laugh at myself after reading your reply....duh waytogo.gif

 

Will try that today.

 

My EVO tracks really well and seems well suited for short exposure EAA

 

Don

KF7DS 


Edited by donsinger, 26 October 2020 - 11:26 AM.



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