To: cfelle2{at}hotmail.com, atm{at}shore.net
From: mdholm{at}telerama.com
Reply-To: mdholm{at}telerama.com


Chris,

You didn't give the zonal radii, so I had to guess at them.  I guessed 30
mm, 71 mm and 95 mm.  I plugged the numbers into Sixtests.  If my guesses
are near correct, and your mirror is accurately represented by your
measurements, you have a sphere with a Strehl ratio of 0.999 with an RMS
error of 1.5 nM and P-V error of about 5 nM.  5 nM is about 1/100 wave.

IMHO, before you touch this masterpiece again, you should do lots of tests
with more zones, average the results, determine the standard deviation of
the zonal measurements, run both the individual tests results and the
average through Sixtests and then sit back and look both at the Sixtests
results for the individual sets of test data and for the average.  If the
average +- one or two standard deviations is within the error budget for
the testing you want to do with this mirror, then QUIT while you are ahead,
because, if these numbers are real, you are a long way ahead of most.

Also, please use a Couder mask for your tests.  It is pretty hard to judge
those shadow positions without one.  I would actually use two masks with 3
or 4 zones each.  The time spent measuring the extra zones is well rewarded
by the extra certainty about the test result.  You can get my Windows
program for Couder masks at http://www.atmsite.org, or see Nils Olaf
Carlin's web site on Couder mask dimensions (also referenced at ATMSite). 
My program will print the mask pattern for you, so you don't have to get
out your compass and ruler.

Also, build or buy a very sturdy, well fitted storage and shipping box for
this beauty, because you sure don't want it damaged!  If you have to pay a
carpenter to build you a good box, consider it money well spent.

Mark Holm
mdholm{at}telerama.com

--- BBBS/NT v4.00 MP