Re: [ATM] Amount of Under Correction??

["Bob May" <rmay@nethere.com>]

For a plate glass mirror like that, I'd probably consider about a
three percent or so undercorrection but since you bought pyrex,
why do you think that you need undercorrection?  Pyrex is an
essentially zero expansion glass so it isn't going to be moving
about anywhere near as much as a plate glass mirror would.  If
you think that you can put in a 0.1 percent undercorrection, be
my guest!  That is about the amount needed to "keep" a perfect
mirror surface under a cold inght.  Then you need ot figure out
how to support that mirror as the typical threee point cell won't
hack that load for accuracy!
Bob May

rmay at nethere.com
http: slash /nav.to slash bobmay
http: slash /bobmay dot astronomy.net


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