Quote:
Originally Posted by Aster
I was thinking of supporting it on a continuous ring just inside of the outside diameter, around the 90 - 95% zone.
Leaving as much of the back exposed to the air as possible.
Mirror is only 31mm thick, moulded pyrex. Will it deform,sag to much from a parabola ?
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Hi Alex, without knowing your specs exactly I'd say you would end up with a slightly overcorrected figure just supporting at edge.More important it will warp in odd ways when not pointing vertically .
Its best to keep the ring surface area minimum so it doesn't warp the mirror. My 14" uses about 18 X 1 inch square pads in a 60% zonal ring. Good industrial Velcro too you get cut off a roll at the hardware , not the litle packets.
If Silicon don't let it compress under1/4".
Remember it means the cell will have to go under the tap too when you wash the mirror, which is why I like Velcro. It has a little give in it and yet holds collimation really well. I think another IIS guy used it on his 12" GSO with great results. getting the mirror off takes good nerves . You need to apply a wooden wedge under one side and keep up a sustained force for a while to make the velcro come apart.