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Figuring The Sagitta

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Posted by Lee D. Crenshaw on February 24, 2002 01:53:02 UTC

Hello,

I'm trying to figure out the sagitta using a formula I found ( Diameter divided by 2, squared, divided by 4 times the focal length ). What I want is about an F/9 focal length. I get a depth of about .05", or about 1/20 of an inch. Does this sound right for an 8" mirror ?

I've got about a 1/16" already, after about 3 hours of grinding with a half diameter iron tool. Does that seem too fast ?

AND, last but not least, if both those calculations are correct, then I'm about 80% there, and it's time to make the tile tool right ?
So, what do you think ?

And thanks ahead of time !

Lee

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