[ATM] Back to pushing glass

[edwski@comcast.net]

Greetings ATM group,
It has been awhile since my last adventures in glass pushing(about 3 years+).
But, I'm back for another dose.
I always seem to be between projects, never seem 100% done and there is always something new.
On the glass pushing front, I recently purchased a Meade 16 dob, yes one of those monsters.
The mirror needs recoating(white/gray blotches on the coating). So, I had a Ronchi done at the National Capital Astronomers, NCA, mirror/atm workshop, Guy Brandenburg's group. The mirror looked very undercorrected, ran out of time and didn't get to a Foucault.  I then had the mirror checked by Northern Virginia Astronomy Club(NOVAC) member Mike Mills. Mike is great at atm projects and does some great testing too.
He made an image of the Ronchi and then performed a digital Foucault, here is the text:  "got a chance to test your mirror tonight.  A test report PDF is attached that shows it came out at about 1/3.6 wave P-V (1/13 RMS) on the wavefront with an expected Strehl ratio of 0.79.  It doesn't quite pass, but it's the best of the three Meade 16" mirrors I've tested.  The center is way high, just like in the other two.
I used your mirror as my guinea pig for trying out Suiter's digital Foucault method (basically, you take knife-edge pictures of the mirror at several known longitudinal offsets and then analyze the images to figure out which zone of the mirror is nulled.)"

The image and PDF are at:
http://home.comcast.net/~edwski/astropage.htm.
I'll probably make a full sized lap, bring it back to a sphere and then work on figuring it.
It's fun to be back working on mirrors again.

Enjoy the sky
Ed Witkowski
Woodbridge, Va
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