Edge 8" Image Train with OAG and ASI2600MC Camera

Michael Miller:
This video in AstroBlender's Back-Focus 101 series should be helpful:
https://www.youtube.com/watch?v=mwlj6VC10yM&list=PLE-H5M8vFOdL7xkde6ReVttN12VoGSdrc&index=9

Mike

Thanks Mike.

The back focus requirement is not based on the camera, but rather the scope/corrector/reducer.

For the 8" EdgeHD, the proper back focus distance is 133.35mm when running natively at f/10 and 105mm when you've got the reducer. The manual shows you how to attach a DSLR. It mentions using a T-ring adapter and a T-ring. Well, the Celestron T-adapter is 78mm and the typical T-ring/DSLR gets you 55mm. Thus, you get 133mm . Notice that 55mm number? Looks pretty similar to what ZWO offers in various rings/adapters with their cameras. But again, it's irrelevant to the CAMERA and has everything to do with the scope.

So, since you've also got the OAG, you're going to need to consider that part, along with whatever adapters in getting you to the required 133mm value. The OAG manual shows a very clear diagram of how to setup your imaging train. You just substitute the DSLR/T-ring for your 2600/adapters.

For informational purposes only (since I shoot with a 294MM Pro) here are my two image trains (both with and without the 0.7x reducer). First, without the reducer:

EdgeHD -> T-adapter * -> female m42 adapter -> OAG -> male m42 adapter -> 11.55mm ring -> EFW -> 294MM Pro

With the reducer:

EdgeHD -> SCT adapter -> OAG -> male m42 adapter -> 11.55mm ring -> EFW -> 294MM Pro

The * above is because I use the "long" part of the 8" Edge T-adapter. For the 8" EdgeHD, Celestron's T-adapter is a two-piece affair. Together, it is 78mm as I described in the first paragraph. However, you can unscrew it and you'll end up with the "long" piece being 49.3mm. You do not need to do this. I do it because I switch between imaging native at f/10 and imaging reduced at f/7. With it setup in this fashion, I keep the camera/wheel/OAG exactly the same. In other words, I don't need to mess with the OAG camera spacing when going from f/10 to f/7.

Jerry Gerber:
Thanks Jonny for that information, it's very helpful. As soon as the OAG arrives I'll figure out what adapters I'll need for both f10 and f7 operation. 

Did you get the backfocus numbers from Celestron or did you figure it out through trial and error?

Directly from Celestron. Their white paper describes the back focus and the manual for the reducer does as well. Here's the link to the 0.7x reducer for the 8" EdgeHD: https://s3.amazonaws.com/celestron-site-support-files/support_files/94242_reducer_inst_sheet.pdf