From: "Bob May" 
To: "Jack Schmidling" , 
Cc: "Dennis Persyk" 
Reply-To: "Bob May" 


The Schmidt astrograph is only one way to do the job.  Bernard Schmidt did
the vacuum pan method as well as the whole idea of a fast astrograph and
most of them have been done at faster ratios than those on that page. The
Mak corrector system will also do about the same thing as the thin oddly
shaped Schmidt corrector plate will do but it needs a lot more glass to do
it.  The good thing is that it is done with spherical surfaces so it is a
lot easier to do on a production line, the Meade and Celestron products
aside.
I will note that there are other designs for doing the same correcting of a
spherical primary mirror to properly focus the incoming light to a proper
point as the two corrector systems mentioned above.

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