[ATM] RC cass secondary and starlaps.

[Jim Burrows <burrjaw@earthlink.net>]

I have finally, FINALLY, gotten the wavefront RMS down to 32.1 nm on 
my 10" RC cass (one test only, more to come, and if they agree, on to 
a star test).

I've been using starlaps for figuring the secondary, many, many laps 
with 4 petals and only very small RMS improvements.  3 or 4 spells 
ago, I tried 3 petals - WOW, big difference!  The RMS went from 106 
down to the 32.  I'm guessing there might be a little physics going 
on here - if one petal of a 4-petal lap wears down, the mirror-lap 
contact may be determined by the other 3 petals, like a stable 
3-legged stool, but then the overall shape of the lap would be incorrect.

         -- Jim Burrows
         -- http://home.earthlink.net/~burrjaw
         -- mailto:burrjaw@earthlink.net
         -- Seattle N47.4723 W122.3662 (WGS84)

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