To: lsayre{at}apk.net, atm{at}shore.net
From: mdholm{at}telerama.com
Reply-To: mdholm{at}telerama.com


Larry,

I really think 1.50e-6mm RMS is an unrealistically tight spec.  2.5e-6 mm
RMS is 1/200 wave, very roughly equivalent to about 1/40 wave P-V.  David
Lewis recommends about 1/120 wave RMS, very roughly equivilant equivalent
to 1/20 wave P-V, to as the spec for the mirror cell.  I think that if your
cell introduces no more than 1/2 as much deformation as you have residual
from figuring errors, you are in pretty good shape.  Since 1/20 wave P-V
and/or 1/120 wave RMS are pretty tough figuring standards, it is likely
that 2.5e-6 mm RMS will be good enough for almost all ATM Mirrors.

There is a discussion of diffracton patterns and Strehl ratios versus
mirror cell residual deformation at my web site
http://www.telerama.com/~mdholm/atm/cells/index.html

The discussion is for a smaller mirror, but Strehl follows RMS pretty
closely, so the discussion can be scaled pretty reliably by just using the
RMS value.

If you want more help with Plop, let me know.  I have a 36-point setup from
John Dudgeon.  I haven't got it on my mirror cell web page yet, but could
either forward it to you or run it for you.

Mark Holm
mdholm{at}telerama.com

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