Reflecting a laser with a mirror... is there a limit to the power level?

sophiecentaur

Absolutely right. I think it must be down to my h t c and predictive txt!
So even Hubble uses Perspex- despite how heavy it is? Interesting.
[edit: I have to apologise; I mean Pyrex again.]

Redbelly98

Uh, you said "Perspex" again :-)

Bobbywhy

My Questar telescope has a Zerodur mirror. I paid a premium to buy it, but the results are fantastic!

Zerodur, a registered trademark of Schott Glass Technologies,[1] is a lithium aluminosilicate glass-ceramic[2] produced by Schott AG since 1968.[3] It has been used for a number of very large telescope mirrors including Keck I, Keck II,[4] and SOFIA. With its very low coefficient of thermal expansion it can be used to produce mirrors which retain acceptable figures in extremely cold environments such as deep space.
http://en.wikipedia.org/wiki/Zerodur

Redbelly98

Ah yes, I forgot about Zerodur.

After some searching around, I found out that the Hubble's primary mirror is made from Corning's Ultra Low Expansion (ULE) glass, with α = ±0.03×10^-6/°C.

That's comparable to Zerodur, and about two orders of magnitude lower than Pyrex (3×10^-6/°C).