Help, please - something is wrong with my integration 🙁

Ordered.  It's not that much money and I can send it back but suspect it will help in any case.

Now, any speculation on why my flats do not eliminate this vignetting -- or, for that matter, the big defect that is on my non-focal-reducer image of Andromeda above?  

Thanks much!

- Rich

At the moment not really sure no, these are very difficult to pinpoint as it's hardware specific, I can only suggest some things that might help but I would also advice to check with someone local to you (like a observatory) to go over the setup maybe.

Well, I received my 2" adapter, and I'm sorry to say it did not help with vignetting on Andromeda.  Perhaps slightly, I could dig up the image.  However, the 2" adapter is a superior setup for regular use and I will be using it in the future. 

I suspect that my issue is that I got the cheapest available field flattener/focal remover.  I should have spent the extra money for the Celestron one designed for my sct.  Lesson learned. 

Thanks!

- Rich

PS - in general, I would say that Andromeda is not a good target for my setup with it's long focal length.  It is so huge with nebulosity everywhere that it highlights vignetting and makes background subtraction very difficult.  

Oh that's a pitty, good it does help in the setup though! Keep us posted if you get to a better result, would be good to know.