Re: [ATM] Flat grinding the back of the primary mirror

["Mel Bartels" <mbartels@bbastrodesigns.com>]

> I have two - six inch mirror blanks I'm about to grind (f/10 or f/8 -

> that some "purists" would fine grind the back flat, and even grind the
> side, with differing opinions on the merits.

For large thin mirrors, grinding the back flat is necessary.  Otherwise, the
varying thickness of the blank causes astigmatism in the front surface.

For small and medium mirrors, or mirrors that are 6:1 ratio of diameter to
thickness, do not grind the back flat.  There's nothing to be gained.

Mel Bartels


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