Re: ATM An Old TMs Simple Query

["Matt Considine" <matt@considine.net>]

The back can be curved - it doesn't need to be flat.  In fact, if half the required curvature is 
put on both sides of the plate, you avoid having the back of the plate act as a flat reflector 
for ghost images.

If I understand that design correctly, shouldn't the figure of the "secondary" spot have the 
same polynomial coefficients as the corrector surface it sits upon?

Or are you putting two different curves onto the plate?  Wouldn't that be tough to make?

Matt
(who hasn't made a plate yet)

> I have wondered for some time "Why the Schmidt always had a flat
> corrector plate?".  If it could be curved, the backside could
> then be used as a Cassegrain secondary, similar to that used in
> the Gregory Maksutov.
> 
> I have added something like what I am asking at:
> 
> 	http://users.rcn.com/rflrs/newsch1-04x.len