Re: ATM An Old TMs Simple Query

["Richard F.L.R. Snashall" <rflrs@rcn.com>]

Matt Considine wrote:
 > 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?
 >

The secondary side of the corrector in the example is spherical.  The
Schmidt correction is on the front surface.  It is the primary that
is also figured in the example.  If the separation between the primary
and secondary is increased (to about 401.25 mm), the primary can also
be made spherical.  This makes the EFL over 3 m.

		Rick S.

 > Matt
 > (who hasn't made a plate yet)
 >
 >
 >