From: "CSC" 
To: "Atm" 
Reply-To: "CSC" 


Garth:
Replacing a tool late in the fine grinding stage would create some
problems, I'd guess.  High or irregular tiles would plow the edge until
they found the curve.

Reportedly, Jean Texereau believed that one could not reliably figure the
edge, and recommended masking it.  Maybe 3/8" is more than he meant. 
Either way you go, it will be a great scope.

The edge cannot be left turned in the optical system, as it does affect the
image, and will spoil the view.

colin



-----Original Message-----
From: owner-atm{at}shore.net [mailto:owner-atm{at}shore.net]On Behalf Of Garth
Arsenault
Sent: Sunday, February 09, 2003 9:34 PM To: atm{at}shore.net
Subject: ATM Polishing from center



I am in the process of building my first telescope. It will be a truss
style Dob with a 10 inch f6 BVC mirror.  I am now polishing the mirror. 
The mirror has polished out nicely from the center and has gradually
polished out to within 3/8" from the edge. I have been polishing this
mirror for about 14 hours.  I experienced rapid progress for the first 5-7
hours but have not noticed any progress for about the last 7 hours.  I
understand that a sphere should polish uniformly across its entire surface.
 I had to replace my glass tool about 3/4 way through fine grinding (Don't
ask!) with a home made tile tool. Could this possibly explain what appears
to be an imperfect sphere after fine grinding and leading to my problem
with polishing.  I am looking for some advice on how to best proceed from
here.

Thanks!

Garth Arsenault

PEI, Canada

arsenault{at}upei.ca

--- BBBS/NT v4.00 MP