To: atm{at}shore.net
From: "James W. Burrows" 
Reply-To: "James W. Burrows" 


At 04:58 2002-12-17 +0000, kwhitefire{at}juno.com wrote:

>Now, if I can plot a mirror design that eliminates all three to a
>reasonably small quantity, this would be Something Good, right?
>
>How close to zero coma, zero astig, and zero focal plane curvature must I
>get for a design to be effectively aplanatic?

Zero coma, zero spherical aberration (not astig) = aplanatic.  Richard says
an R-C cass with secondary magnification of 1.6 will also have a flat
field.  I know that positive surfaces bend the field one way and negative
the other, so it is indeed possible that there's an R-C combination that
has a flat field, but I'm not sure about the numbers.

         -- Jim Burrows
         --              mailto:burrjaw{at}earthlink.net
         --              http://home.earthlink.net/~burrjaw
         -- Seattle      N47.47233, W122.36620 (WGS84)

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