Should I clean my mirrors.

[Tandum]

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.

[Geoff45]

I'd wash it. I did mine about a fortnight ago and it made quite a difference.
Geoff

[Tandum]

I decided not to. I blew out the insects and cobwebs with a compessor on a water trap instead. None of my images show diminished light in the center of the field, it must be an eyepiece problem. As I use this scope for imaging, all eyepieces I have are cheap crap. I don't need good ones. Thanks.

[Glenhuon]

Seems like the eyepiece, I have a 20mm cheapy that does that too.

Cheers
Bill