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Thanks very much for your response, Paul. That'll take a while to fully digest!
I'm also using a Moonlite and a GPU coma corrector (TS branded, but it's the GPU). This morning I played around with a few different adapters and now have the spacing at about 55.7mm, according to the calipers, which is hopefully close enough. I doubt I'll get any better unless I go down the precise parts path, which is always expensive... and even then there's measurement error so I couldn't be too sure it'd do more good than harm!
Everything in my imaging train (including the focuser -> coma corrector connection), is threaded, except for the TS OAG -> filter wheel connection, which uses a crappy system with three thumb screws--that may be causing tilt but I did my best to apply pressure and keep it square when tightening it.
When my camera is focused the focuser's 2 inch draw tube is only racked out about 5-10mm. In fact, I may need to move the primary mirror further up the tube as the GPU corrector is inside the focuser's draw tube and actually sticks into the OTA by about an inch when it's at focus.. when looking at out of focus star images you can see a nice flat side on all of the stars which I assume is the corrector.
I hope I don't have any astigmatism, but I did look at how the secondary is connected to the holder this morning and it seems to have a smear of some kind of glue / adherent so I may be in the same position as you there... hopefully not though.
I measured, using calipers, the distance between the coma corrector's adapter and the face of the camera's body and that seemed to be consistent, though I was restricted in where I could measure, which suggests either focuser or sensor induced tilt... I should be able to verify by rotating the OAG -> filter wheel interface and seeing if the tilt shifts with it.
Thanks again, Paul!
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