Charlie and Josh braved the colder weather and my unheated garage for another good ATM session yesterday. Seriously, during the winter it can be cold in my garage as it faces north and so never gets sun. If you do make it to an ATM session during the winter, wear thermals and warm socks! Josh brought his newly acquired set of Ronchi gratings as well as knife edge testers. All of us viewed his 8" mirror with the knife edge and then I showed how to perform a Foucault test. Josh got the hang of it very well and we traded turns taking measurements of his mirror using a five zone Couder mask. The readings were very consistent and so we used my favorite data reduction program, fig34, to crunch the numbers. His mirror tested to 1/8 wave (P-V on the wavefront) with a Strehl ratio of 0.975. A very respectable mirror. However, he can improve on that and in the process gain valuable experience. The mirror has a slightly high center, and the outer zone is focusing a little short. Those are the areas he will work on with a sub-diameter lap. Josh also brought a 4" Pyrex blank he got from Willmann-Bell that he will to use to make a finder for a larger scope. We poured a dental stone/tile tool for him to use to grind this blank to a nice 4" f4 mirror. Currently, I am working on a ball mount for my 4" f4 mirror, another 4" f4 mirror that is fully polished and waiting to be figured, and two 6" f4 blanks that I am starting to fine grind. The idea is that by next month I will have three blanks to be figuring at the same time, I know, I'm a glutton for punishment. At least they are small mirrors. My thinking is that by then I will understand how to make mirrors by machine and then will start on larger (8" and 10") mirrors. The next session is on Dec. 10th from 9:00 AM to noonish. As usual, email me off list at mat.hutchings@siemens.com <mailto:mat.hutchings@siemens.com> and I will give you directions to my house. Mat ---------------------------------------------------------------------------- This message and any included attachments are from Siemens Medical Solutions and are intended only for the addressee(s). The information contained herein may include trade secrets or privileged or otherwise confidential information. Unauthorized review, forwarding, printing, copying, distributing, or using such information is strictly prohibited and may be unlawful. If you received this message in error, or have reason to believe you are not authorized to receive it, please promptly delete this message and notify the sender by e-mail with a copy to Central.SecurityOffice@siemens.com Thank you