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Re: [ATM] RC cass secondary and starlaps.

Congratulations Jim!
   
  When you feel that you have nailed the procedure down, please write it up so that we can share in that knowledge. Bill Mariott and I are going to follow the same path as you except we are going to be making 20 inch RC cass's with Fused Quartz elements. You wouldn't want to try a big one later, or would you? I still have a 20 inch FQ blank and smaller pieces available.
   
  Ken Hunter
  

Jim Burrows <burrjaw@earthlink.net> wrote:
  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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