Quote:
Originally posted by bytor666
People need to not be so fussy about what the mirrors are made out of, heck even the older 100 inch mirrors were made out of PLATE GLASS with bubbles all inside of it and those were amazing telescopes.
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But the Hooker telescope is kept in an insulated dome so that there is little temperature variation. This is slightly impractical for us. Stargazers don't want to have a two hour cooldown time after bringing the scope from indoors. Pyrex will still have a long cooldown time, but the strains during that time are less than half of plate glass so the distortion won't be as bad.
Of course, once equilibrium is achieved the figure is what matters.