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Re: [ATM] Cassegrain vs. Gregorian



Michael Peck wrote:

 > Your conic constants are slightly off of the aplanatic solution. I get
 > (-1.083, -4.839) for the Cassegrain primary and secondary; and (-0.985,
 > -0.508) for the Gregory. The difference is a few thousandth's of a wave
 > at the edge of the field.

In fact, the RoCs are tweaked too.  The difference gives the
aplanatic solution better performance inside the half-field
point, but the optimized solution is better outside the
half-field point.  As you say, though, the difference isn't
much.

Incidently, it took me a while to dig back into R&vV to find
the aplanatic equations, but I couldn't find them for a
Gregorian, so I derived my own set:

	http://users.rcn.com/rflrs/twomirrors.htm

-- 

Rick S.

http://users.rcn.com/rflrs


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