Imaging train using ATIK 383L+ mono!!

[mewein]

Hello all,
I am planning on using ATIK 383L+ mono with EFW2 filter wheel and an OAG (not sure which one to use). I will be guiding using SBIG ST-i guide camera.

The challenge that I am facing is my back focus requirements are 55mm.

Using the ATIK 383L+ and the EFW2 the back focus is around 17mm+22mm = 39mm. I am not sure I know what is the thickness of ATIK's OAG (I believe it is 24mm). If it is indeed 24mm, then I don't suppose I will be able to use it as part of my imaging system. In that case, what are my options? Over here in the US, Orion sells a thin OAG that has a thickness of 10.5mm. That should put me at around 50mm leaving me with 5mm which I am sure I can get a spacer for.

Am I missing anything? I am not sure how to connect the Orion Thin OAG to the EFW2 and not sure what space that will take up.

Any help will be greatly appreciated.

Thanks,

[vince]

Hello,

The Atik OAG has a backfocus of 24 mm as you mentioned, the depth of the OAG is such so that the main camera and filter wheel together allow the guide camera to become parfocal with the main camera without protruding too far from the QAG. You can use a narrower OAG but what you take off in OAG depth you will be adding to how far the guide camera is away from the OAG body and possibly introducing flexure. I assume you are using a reducer / flattener with your system?

Best regards
Vince