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

[info@stathis-firstlight.de]

I fully agree with Mel.

In Germany (and other European Countries as well), the Borofloat of 25 mm
(1") thickness became very popular, as it is easily avialable at a good
price. So many mirror makers push the limits and make large mirrors out of
it.
Practice has shown, that it is nesessary, to grind the back flat for sizes
larger than 14-inch, particularly, if they are worked Tool on Top. I know
some cases with 18" and 21" which showed astigmatism. After grinding the
back flat and polishing for a while the astig disapeared.

Stathis
www.stathis-firstlight.de


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