Re: ATM Polishing figure

["Bob May" <bobmay@nethere.com>]

The pits need to be polished out before you really start doing any
definitive tests with the Foucault Tester.
A interesting test can be done by putting the slit wide (or just using a
bright LED) at the ROC and you will see that the surface will be bright and
probably has a dark center zone.  You don't want to see the returned beam
but rather look from about a half inch or so off from the returned light.
The light that you will be seeing is from the pits that are still there and
when the glass ends up being dark with an occasional spot that you can move
around (dust in other words) you are pretty much ready to start looking for
real at the surface.  Lumpy surfaces that aren't a figure of rotation are
generally indicatave of not rotating the mirror and tool enough.  If you do
have a lumpy figure of rotation on pitch then you need to do a good pressing
and mostly short strokes with some longer ones to blend in the zones.
Bob May
My new web space address is http://webu.wigloo.com/bobmay/ or
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and my new email address is bobmay@nethere.com
Bob May