[ATM] Baffling a Gregorian and corrector plate fabrication.

[Douglas S Angle <Douglas.S.Angle@can.dupont.com>]

I'm contemplating building a Gregorian, and I've been looking at different 
design considerations.  I've browsed through the archives, read Rutten & 
van Venrooij on the subject.  One thing I can't figure out is how to 
baffle such that stray light can't get from the entrance aperture to the 
eyepiece.  There's an article in ATM about a newt-cass-gregorian 
telescope, but the article doesn't address baffling at all, and the 
pictures don't look like there's any attempt to baffle.  I did a full size 
drawing, and I can't see how to catch more than about 1/2 the stray light. 
 For reference, my design was:
primary diameter 16"
primary focal length  64   f/4
secondary  diameter 4"
distance of focus behind primary 15"

I would be interested in hearing from anyone who has built a gregorian, or 
advice on how to solve the baffling problem. 

I also considered a shorter focal length primary combined with a corrector 
plate.  I understand the principle of the Schmidt camera, where the 
corrector is placed at the center of curvature, and can be made using the 
vacuum pan method.  If I were to move the corrector plate towards the 
primary, is it true that the I can't use the vacuum pan method anymore, 
because the shape is now different?  For that matter, is there any 
difference between a corrector plate as used in a schmidt camera, vs one 
used in a compound telescope so that the primary can be left spherical?

Thanks all.
-Doug

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