[Tandum (Robin)]

I got hold of a Bahtinov Mask just before going up to Barambah and found I could only use it on really bright stars like Alpha Cen. Trying to focus on Fomalhaut produced a poor result which is not what I expected.

Tonight I have been practicing drift alignment, and I really need the practice, but I've noticed that when bringing a star into the central FOV, it gets quite dim. I'm losing over 50% of my light in the middle of the field. Moving a dim star from the edge of view into the center of view, that star will vanish.

I can see eggs and crap from insects on the primary mirror, should I strip the scope and wash the mirrors or is this collimination? If I pass focus through a star it is perfectly round each side of focus. It is a VC200L.