Below is an abbreviated report of the "super ATM session" held on 5/4/12 and 5/5/12 at the Hutchings optical shop (my garage). If you would like to read the longer version, go to the astronomy in Utah forum at: http://astronomyinutah.forumer.com/index.php then go to the ATMing in Utah forum, then the subject is ATM report. The first "super ATM" session is now history, and I for one had a great time! Charlie, Mike, Jeff, Jeff Porter, Kristen, Jay, Josh and I were the attendees. Friday evening we star tested Charlie's 13.1", f9 mirror in a test bed (old 17.5 Coulter dob assembly), Mike worked his 8" mirror projects and my son, Jeff continued his 8" by grinding with 180 grit. Charlie's mirror ended up being astigmatic which takes us to the next day... On Saturday, we started off by looking for strain in Charlie's mirror. We used a laptop monitor as a source of polarized light which shined through the mirror then we looked at it through a polarizing photo filter. It showed that indeed there is strain in the blank. To really fix the blank, it should be annealed, then the back ground flat, and then taken back to 320 grit until a good sphere is obtained, then worked in the normal ways all the way to slight polish, then it can be star tested again for astigmatism. Since we had the test set up for strain, we tested a lot of glass. Josh tested his 4" and 8". The 4" had the "cross" pattern that indicates a stressed mirror. I tested probably 10 pieces of glass including Pyrex and plate and surprisingly, to me at least, was that all the plate glass was strain free. Some of the Pyrex blanks had a little strain, but nothing to be worried about. I was very happy that my new 21" blank was stress free. Josh poured a new pitch lap for his 8" mirror. He will continue that project by polishing it out fully. As you can see this was a fantastic "super ATM session". I am up to doing it a couple of times per year, so stay in touch for another like this in the fall. Happy grinding! Mat This message and any attachments are solely for the use of intended recipients. The information contained herein may include trade secrets, protected health or personal information, privileged or otherwise confidential information. Unauthorized review, forwarding, printing, copying, distributing, or using such information is strictly prohibited and may be unlawful. If you are not an intended recipient, you are hereby notified that you received this email in error, and that any review, dissemination, distribution or copying of this email and any attachment is strictly prohibited. If you have received this email in error, please contact the sender and delete the message and any attachment from your system. Thank you for your cooperation