RE: ATM astigmic mirror.

["CSC" <optic@gwi.net>]

.002" is not much.  Your testing skills are way up there now.


Good time now to do a bench star test.
Use a pinhole as small as you can, and a hi power eyepiece.
The star test diffraction patterns should be round, or perhaps slightly oval
if the setup is off-axis. As with other tests, an irregular image rotates
with the mirror.

The in focus image will be the fine pinhole with diffraction rings.

Extrafocal images are the same inside & out for the sphere.

Is the image crisp or weird? That hourglass shape may show itself in the
extrafocal star test, but may not be enough to degrade the image at focus.

I'm in love with the star test and used it a lot when testing spheres.  I
tried to test & polish out a weird shape I created by heavy TOT polishing
with a 3 point mirror support.  I couldn't polish it out after many hours.

colin