ATM Advice on Large Spherical Mirror?

[David Sleeter <d.sleeter@verizon.net>]

Hi Folks:

I bought a large mirror today at a surplus yard. Here are the specs.

It is 16-1/2" dia., F-2.5 (40" focal length) with a central perforation
of approx. 5" dia. The blank is molded of a clear glass, probably Pyrex?
It is 3.5" thick at the central hole, and 1-1/4" thick at the outer edge
with 8 massive radial ribs connecting the center to the edge.

It came with a machined & anodized aluminum center-mount (like
Celestron) cushioned on the optical surface with a cork and a teflon
washer, but no padding at the rear. 

A focault knife-edge test results in instant, uniform graying across the
mirror's entire surface; looks like a good sphere. I made a rather crude
100 line-per-inch ronchi grating with my CAD program, a 600 dpi laser
printer, and a sheet of clear acetate. The ronchi lines look reasonably
straight, but it's hard to get an excellent read, because my Focault
tester uses a cheapo "grain-of'wheat" bulb. The image of the filament
shows through the pinhole, and it distorts the appearance of the ronchi
lines. 

There is a 2" wide, conchoidal chip in the back surface of the mirror
near the central hole, but it is shallow (1/4" deep). That puts it 3"
back from the optical surface; probably too far to cause any distortion.
There are 2 smaller chips around the 8-1/4" dia. edge of the central
part of the mirror blank, but again, they are at the rear of the mirror,
and 2" to 3" back from the optical surface. It is aluminized, and the
coating is in useable condition. 

Does this mirror have any ATM potential, or is it just another
ant-burner?

Dave Sleeter