From: "Jack Schmidling" 
To: 
Reply-To: "Jack Schmidling" 


I am having trouble sorting through all the comments and advice so I am
going to take a different tack under the assumption that a picture is worth
a thousand words.

The only thing I have handy are some pictures I took of M3, with and
without the Ross coma corrector.  This happens to demonstrate the point I
have been trying to make regarding the correlation between diagonal shadow
and coma. I will try to complete the picture tonight but for now, got to:

http://schmidling.netfirms.com/oofcc.jpg

Note that the left hand image with the coma corrector shows the diagonal
centered in every star, right out to the edge and the annulus is evenly
illuminated all the way around.  Never mind for now the fact that the stars
are not round but I would be interested in knowing why later.  I won't
waste the bandwidth posting the infocus image but there is no coma and
every star is round.

The right hand image is without the CC and you will note that only the
stars with the shadow centered display evenly illuminated annuluae.  The
infocus image demonstrates that the bright spot on every star is the head
of a comatic image.

js

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