From: "David Lonard" 
To: atm{at}shore.net
Reply-To: "David Lonard" 



Hello Group,

I would like to thank all those who have given advice. So far the biggest
consensus that I have received thus far has been to extend my stroke to
bring the sphere out further to the edge, which I have been doing and seems
to be working well.  I have still been concentrating a lot of strokes along
the more spherical axis since I still think that the edge is higher along
this axis. Along the more hyperbolic axis, I am using a longer W (or V?)
stroke.  I have an updated ronchigram photo at

http://www.geocities.com/lonard3/mirror.jpg

I have also made what I hope is a more reasonable star lap as was
suggested.  Several of you have said that I should wait on the star lap,
but I have tried using the full lap and things go wildly oblate spheroid
when I do so. At any rate, the ronchi bands are getting rather straight
with this current lap so I think it is currently useful.

To answer your question about machine work Dennis, when the surface came to
polish, the ronchi pattern was packed with multiple nasty zones, too many
and too deep to honestly know if I had astigmatism at that point.  The
12/24/02 image is the product of probably 20 hours of subsequent hand
polishing.  I actually did put it back on the machine, but strong zones
started to return, so I stopped.  To be fair, my machine isn't very
mechanical sound, made out of wood and was practically destroyed during the
violent hogging out process.

I'm sure that there is still plenty of interest in a 20 x .875 inch mirror
so I will try to give more updates.

David






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