[ATM] More on aperture stops

[Jay Kirkland <jaykirk2@compusmart.ab.ca>]

This is a great thread - should really be called "getting the most 
performance out of your scope", or something to that effect. I was just 
driving home and just before the clouds rolled in (for the the 4,772 
night straight [sigh]), I was looking at the fiull moon hanging in the 
reds and blues of twilight and realized that with my right eye, the 
image of the moon was blurred in almost exactly the same way as in the 
illustration for "unobstructed" Mars (and about the same size as the 
magnified Mars) that started this entire thread. Of course, that's my 
astigmatism running away with me. Getting back to the original question, 
the writer said that every telescope he looked thru at that particular 
star party showed the same smeary image. What are the odds of that 
happening?  Could the effect lie with the observer? I wonder, does he 
wear glasses? Was he wearing his glasses when he was using the scopes? 
Does he need glasses? Did any other people - the owners of the other 
scopes - report the same effects? And is there any reason that using an 
off axis mask (smaller image size when the light reaches the eye?) that 
would cause a 3" scope to alleviate astigmatism or other eye effects 
seen in a 10" scope while using the same eyepiece?
   Astigmatically yours,
   Jay
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