[multiweb (Marc)]

I posted this originally somewhere else and didn't get any answer so I'm trying here. Maybe it's more relevent to the photo threads.
I've been trying to improve my images for the past month or so. I purchased a Baader MPCC, a Cateye collimation kit and CCD Inspector. Running my subs through CCD inspector helped me improve my optical alignment and by using the right spacers with the MPCC I managed to flatten my field dramatically. I guess now I'm at the stage where it is "acceptable" but I'm trying to go the whole way. Am I right in assuming that moving the primary towards the secondary up the tube [i.e clipping the primary reflection in the secondary] would improve coma? My reasoning behind this is that the light cone reflected by the primary will be "cropped" by the secondary and not totally reflected so although I'll get less light I'd be using the better part of the primary (no the edges?). Does this sound right? Any toughts? Obviously the scope is a newtonian. 5"/FL650mm F/5. I mostly image at prime focus with a QHY8 [which is a faily large chip] and a 2" nose piece. Thanks for any pointers.