ATM Trying to make a Spherical Surace and It's NOT WORKING!

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

Got a old piece of Pyrex (4") that one of the telescope making group is
working on and he's not getting anywhere in getting it to a nice spherical
surface.  The mirror is about F13.5 so spherical is what he wants.  The
amazing thing here is that he started polishing with a F14.4 so he's moved
the glass curvature a bit!
What the problem is that he has a turned up edge or ring of about 3/8" on
the edge and that turned up ring shape is about .4" of ROC.  The image with
the ring graying out evenly on the Foucault Tester looks like a WW1 helmet
in shape.
Here's the fun part - you can hang the tool over the side of the mirror a
long way and the curvature (he has managed to change the ROC from 118 down
to 112.5 and is about 114 at the moment) changes but the turned up edge is
still there!  Worked with beeswax today and this didn't change anything but
bring the radius out by about 1/4".  Before trying that, tried some local
polishing (didn't succeed because I couldn't hold the mirror properly) on a
powered wheel which did make a very little bit of a ring step (just barely
visible in the Foucault test) but that was all.  It's like the glass has a
ring of something a lot harder in the edge relative to the center area.  I
might also note that all of the polishing for quite a while has been with
the tool on the top.
I might note that I am getting frustrated with this piece of glass and it
doesn't even belong to me.
Anybody got any possible answers?
Bob May
My new web space address is http://webu.wigloo.com/bobmay/ or
http://nav.to/bobmay
and my new email address is bobmay@nethere.com
Bob May