ATM Re: Aplanats II via troublesome Juno X-mailer

["James W. Burrows" <burrjaw@earthlink.net>]

At 04:58 2002-12-17 +0000, kwhitefire@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
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