Re: ATM Polishing out astigmatism

["Bob May" <bobmay@nethere.com>]

First thing is to not use wood for support of a piece of glass as this is a
sure source of astigmatism, as you have found.  Wood (even plywood and
chipboard) tends to expand unevenly with moisture content and this causes
stresses on the glass which doesn't respond to moisture.  Better to use
plaster or metal for doing that work.
It is alright to support a piece of glass on a sealed piece of wood in a
loose fashion that allows for flexing of the wood without carrying that
motion to the glass.  If you are working with thin mirrors then the ability
to steadily support the glass becomes a lot more important.
Bob May
http://nav.to/bobmay
bobmay@nethere.com
NEW! http://bobmay.astronomy.net