On Tue, 26 Aug 2008 22:52:24 -0400, Wayne.B
wrote:

On Tue, 26 Aug 2008 19:31:21 -0700 (PDT),
wrote:

Progress while waiting for Fay to go away. Finished rough grinding
yielding a focal length of 24" (this is a 100 mm diameter f 6 mirror)
and finished the #120 grit and have started on the #180. My
magnifications will be a low of 15 X an a high of about 30X.

How do you know when you have the shape just right?

There are optical tests with simple equipment.

What do use as a blank?

Two discs of pyrex from a mail order house. One is the mirror, one the
tool. You put grit on them and rub them together.

Casady