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

3" ES Focal reducer back focus with a full frame camera

  • Please log in to reply
1 reply to this topic

#1 kes74

kes74

    Sputnik

  • -----
  • topic starter
  • Posts: 37
  • Joined: 10 May 2015

Posted 02 December 2020 - 10:59 AM

Hi folks,

I am currently using an ES 152ED APO for AP.  For those familiar with this scope it utilizes a 3" focuser (default).  My current train is then:

 

2" adapter->Altair Astro FF/FR->Celestron OAG->ZWO ASI071.

 

The above train is not ideal as the celestron OAG is quite wide and takes up a lot of the 55mm back focus (this OAG is from my SCT setup, which has a lot more back focus to play with), also I am not sure whether the Altair Astro 0.8 FF/FR is ok to use in this case (it's from my older ES 102ED APO setup).  I am looking at getting a new camera, probably the newer ASI2400 (full frame colour) camera.  ES sells a 3" FF/FR, which is recommended for this scope ( https://explorescien...d-apo-152mm-f-8 ) and I am looking at getting one of the ZWO OAG's, which are slimmer than the Celestron OAG, but I am not finding a way to get 55mm with this setup.

 

ZWO have made a great start at trying to help people achieve the correct back focus @ https://astronomy-im...tions-55mm.html .  Given a full frame camera I think I need to be using the OAG M68 option so as not to restrict the light field and there is one option the link where that is used with a M54 filter drawer (that I would be needing, living where I do).  The problem is connecting to the ES focal reducer.  The solutions ZWO offer all point to a telescope side that offers M42, M48 or (in the case of M68 OAG) M68 threads.  In my case the ES FF/FR provides a M42 connection, which is very limiting for folks wanting to use anything more than an APS-C sensor.  I suspect the M42 connection can be unscrewed from the back of the ES FF/FR and replaced, but I don't see any adapters that would go from 3" to M68?  So the setup I am thinking of currently would be:

 

152ED -> 3" FF/FR -> ? -> ZWO OAG M68 -> ZWO M54 filter drawer -> ZWO ASI2400

 

Unfortunately I believe the ? needs to be 0 mm.... which might be tricky undecided.gif

 

If anyone is using one of the ES scopes with the 3" FF/FR and an OAG in the mix I am just wondering what your camera train looks like?  Perhaps I need to consider using a guide scope for this setup instead?

 

Wouldn't it be great if there was a website that allowed you to enter your scope, your camera and whether or not you are using an OAG, FF/FR and provided you with the pieces you need to achieve the correct back focus tongue2.gif

 

cheers

 

Matt

 

 



#2 spereira

spereira

    Fly Me to the Moon

  • *****
  • Moderators
  • Posts: 5,060
  • Joined: 21 Apr 2017
  • Loc: Bedford, NH

Posted 02 December 2020 - 11:04 AM

Moving to Beginning DSO Imaging.

 

smp




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