Reply from Larry Manuel:
I too am interested in a 12" f/8 mirror. I like the idea of a thin mirror, not for cost savings, but for cool-down time being minimized. I read recently a statement that telescopes are a mature technology. To me this means that most of what I think of ground breaking innovation has already been tried, and has failed. I've read many times of a thin mirror flexing like a potato chip during testing. A 1:24 thickness ratio is, to put it bluntly, outrageous IF you want better images than a shaving mirror. I think stiffnes is a function of the cube of thickness - this alone spells disaster.
I think your worries of thermal distortion are unfounded. The mirror will only be distorted thermally if the temperature is UNEQUAL throughout. A 1/2" thick mirror will cool down quickly. My 6" f/8 (1" thick) cools in about 1/2 hr, with a tiny 12 v muffin fan. The problem will be mechanical flexure. It will be virtually impossible to eliminate with the support technologies available to a basement glass pusher. If someone gave you a perfectly figured 12" f/8 miiror, 1/2" thick, I doubt if you or anyone else on this ATM 'net could mount it so that it would perform well.
I don't mean for this to be a character assassination at all. If it seems so, forgive me. Your questions are excellent. There are very sound reasons why 1:24 thickness ratio mirrors do not abound except in actively supported new technology observatories.
Please send your observing goals. Super planetary? Low power deep sky?
Please reply. <---- End Included Message ---->