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Originally Posted by Brad Moore
I think I've solved Pete's donut problem. 
I'm alowed to poke fun at him as he is my imaging buddy!  Aint that right Pete. 
The donut is caused by light reflected off the CCD (from the bright star) then bouncing into the rear of the filter, then back onto CCD. The long 30 min sub exposure don't help either.
Cheers,
Brad |
Of course
I thought it might have been a dust mote, but I couldn't work out how it could be so defocused like a dust mote a long way down the optical train, yet so visible.
thanks for that