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Sphericity

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Posted by Robert May on July 25, 2003 17:30:53 UTC

You won't get truely spherical until you are polishing the glass. At 120 grit, the spherometer usually stays within a tenth of a thou. over the full surface and that is good enough at that point.
The big thing to remember is that at the finer grits, doing the light reflection test should end up with an even yellowing of the lamp across the width of the glass when you are nicely ground out and the frosting size is even all over the mirror without any zones of larger frosting.

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