From: "Dave McCarter" 
To: "Vladimir Galogaza" ,
"ATM" 
Reply-To: "Dave McCarter" 


> 1.  Round robin testing of mirrors.
> Goal was to test how result depends on who is testing.

Every tester has his/her limits, based upon the test method, experience, and patience
required to get accuracy with any test method.

> 2. Stressed blank grinding and polishing
> To check if acceptable mirror can be obtained from stressed glass.

Nope. I don't think it can be done. Stressed glass moves over time, warping
the surface so carefully crafted. It might look great after a polishing
session, but soon
it will not. Peter Cerevolo told me of a mirror he once made with
"crappy pyrex". It
polished up just fine and looked good on the interferometer, so he coated it. A few
days later the mirror was sitting in it's cell, when Peter noticed "a
hair wandering
across the surface." He attempted to blow it off, but it would not
budge. He had a
closer look and saw it was a wrinkle in the aluminum coating. On the tester that
wrinkle looked "like the San Andreas Fault". The whole glass
surface had shifted from
internal strain. Lacking a nearby fire hydrant, the glass was executed by
other means.

The time one spends working a mirror is best not wasted on a crappy piece of glass.
Miricles are next to impossible as it is.

Dave

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