[AZ-Observing] Observing Weather this Weekend

If the weather is good this weekend it is because I just purchased a 10" 
LXD75 at RTMC this last Sunday. If the weather is not good it is because 
of what someone else purchased. :-)

I have a question about the optics. When I looked through the scope at 
RTMC, unless I kept my eye close to the eyepiece (a plossel) it appeared 
the field of view got brighter toward the center. When I backed off and 
rotated my eyeball socket (i.e., I moved my head around as opposed to 
just rotating my eyeball), I could see a small lighter disk of light 
following my movement. I know achromatic refractors have the problem of 
a brightness increase toward the center but I do not know if this could 
also be a characteristic of Schmidt-Newtonians. At first I thought dust 
on the secondary might be the cuprit, but it looks good upon closer 
inspection. However, the primary does not look so good. It appears to be 
dusty, but I do not think it is dust. I beleive it is either a bad 
aluminization, or a bad wash job if this is done at Meade after a mirror 
is aluminized. This could cause the field to be brighter because of 
dispersion of the light, and the increase toward the center could be the 
result of vignetting. Does anyone have any insight on what could be 
causing this? I just got back from RTMC yesterday and haven't had a 
chance to set it up outside and investigate this more but will do so 
tonight.
Stan



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