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RE: RE: RE: Help Again,

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Posted by Robert May on August 3, 2000 16:40:59 UTC

Here`s the general formula for finding the Sag.
Sag= Rad. Mir. curve - square root of ((Rad. Mir curve) squared - (Rad. Mir surf.) squared). If you want to measure with a spherometer, the radius of the spherometer is used rather than Rad. Mir. surf. Now go figure what you want to have.
When you grind you first mirror, it`s almost don`t bother to really measure the ROC until you have it polished and ready to figure. At that time, you can measure it on the Foucault Tester and get it right to as tight as you measure although to 1% is more than good enough.

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