[Wombat68 (Trevor)]

I have a Skywatcher 8" Dobs scope.
To be honest I have always avoided doing collimation but after looking at a 'how to' on youtube it seemed fairly straight forward.
Collimation was as per the video - pretty easy and straight forward to do.
I did notice however that the primary mirror seemed noticeably dirty.

Would love some advice on the best way to clean this mirror would be.