So, what am I doing wrong :-)

[szymon]

LP filter due to arrive tomorrow! Expect clouds for the next few days, right in the vicinity of M31 :-)

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[Astrosurf]

Yay! With a bit of luck you'll manage to get longer subs for the arms. Is this the Clip-in filter?

[szymon]

No, it's a standard 2" Skywatcher LP filter. I have an Opteka t-ring which is threaded for 2" filters on the camera side, and it achieves prime focus with the 200p, so I am hoping that it will still do so with the filter attached (FLO have been great as usual and said that I can return the filter if it doesn't fit).

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[Astrosurf]

I wanted the same filter some years ago but they said it wouldn't work with my set-up. Maybe your T-ring is a new thing, but I'm not very knowledgeable on gadgets! Good luck!