Chronology Current Month Current Thread Current Date
[Year List] [Month List (current year)] [Date Index] [Thread Index] [Thread Prev] [Thread Next] [Date Prev] [Date Next]

[Phys-L] Re: telescope mirrors

Sorry, telescope mirrors are almost always made by grinding one piece of
glass over a another piece of glass or softer material with the use of an
abrasive slurry. (Many books on Amateur telescope making)
The use of a rotating mirror (mercury) was proposed several decades ago,
but was not practical because of he necessity of eliminaing all vibrations
which produce ripples on he mercury surface.
to confess my own sins, I once tried to form a parabolic reflector using
epoxy, but ended up spraying epoxy all over the lab.
I believe that there are some experimental mirrors that use a thin film of
mercury over a near prabolic spinning form.

Al Bachman


From: Anthony Lapinski <anthony_lapinski@PDS.ORG>
Reply-To: Forum for Physics Educators <PHYS-L@list1.ucc.nau.edu>
To: PHYS-L@LISTS.NAU.EDU
Subject: telescope mirrors
Date: Thu, 26 Jan 2006 22:22:41 -0500

I'm curious about something. I tell my (high school) astronomy students
that reflecting telescopes are made by melting glass and then rotating it
at high speed while the glass solidifies. The result is always a parabolic
surface. How can one show, in simple terms (no calculus), that the surface
of a spinning liquid is a parabola? I am also wondering what the "limit"
would be as the spin rate becomes"very fast." Any help would be much
appreciated!
_______________________________________________
Phys-L mailing list
Phys-L@electron.physics.buffalo.edu
https://www.physics.buffalo.edu/mailman/listinfo/phys-l