🚀 go-pugleaf

There have been a number of anecdotal reports of sagging glass windows.
It occurred to me that large telescopes would make a good test case for
this purported phenomenon. The Mount Palomar mirror is old, massive and
its shape is subject to exacting scrutiny.  If a window can develop a
"noticable" shape change in a few decades, I should think the same
phenomenon would be well observed at Mount Palomar. If noticable means
1 mm, then the Hale telescope (It's at Mount Palomar, right ?) is
sensitive to changes one ten thousandth as great. So if it sagged 1 mm
in 50 years, the optical quality would be affected in a few days.

I know that its elastic response to gravity induced stress has to be
dealt with, so what about its inelastic response?

Lew Mammel, Jr.