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 
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 
cheers
Matt
