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Originally Posted by Mark Suchting
I find when putting the finishing touches on large mirrors that they need to be left overnight and not touched to reveal their final figure.
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Mark,
I respect your comments in this regard and have a couple of questions if I may. Do you find you can work pyrex for longer time periods before having to allow it to cool, compared to plate ? Do you let all mirrors cool overnight or only the larger ones ?
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Its easy for the uninitiated to extrapolate comments to apply to all sizes of mirror so I'm emphasising that as the volume of glass escalates fast in the larger sizes the figuring and using will become far more of a challenge.
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Very true and an easy conclusion to jump to for those that have had good experiences with smaller GSO mirrors. As you point out in the other thread, everything that applies to the smaller mirrors goes out the window with a 16" diameter plate mirror. The 2" thick pyrex mirror in the 18" Obsession can lose heat all night. The day and night time temperature extremes at Lostock, while a severe test of any mirror, showed this. I can only imagine that a plate mirror of this size would never get close to equilibrium under such conditions.
I appreciate your comments on this. The only problem is we confused the hell out of the poor guy trying to buy his 1st telescope.
CS-John B