Quote:
Originally Posted by AstroJunk
Secondly, it's a good idea to do your figuring at least in an environment which matches the temperature that plan to use the mirror. Not such a big deal with low expansion glass, but worth considering.
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Hi Astrojunk
Could you elaborate there ? The relative mechanical dimensions of a glass blank are the same regardless of its temperature. Are you referring instead to the practise of undercorrecting a plate glass mirror to allow for possible overcorrection condition as the ambient temperature falls and the optics can't keep up, when in use under the night sky ?