Re:ATM Beyond the fan

[Fabio Pettinati <fabio@voreas.com>]

My primary concern would be that the heat that is pumped away will rise and might go in the optical path creating turbulence (a contrarian view would be that such heat might help disrupt any stagnant layer close to the primary.

My other concern has to do with how localized on the mirror itself the cooling would be. There needs to be a way to distribute the cooling effect uniformly over the entire back surface of the mirror. An off-the-cuff idea would be to have an array of floating metal disks touching the back surface of the mirror, perhaps with some thermally conductive compound ensuring good thermal conductivity. The disks would need to be slightly pushed against the back surface of the mirror by small springs or something. Then thse disks would need to be thermally attached to the cool side of the Peltier junction so that the whole ensamble is a "giant" active heat sink.

Perhaps an even better solution would be to use a heat pipe of sorts. I just found this company on the web (http://www.novelconceptsinc.com/index.htm) that sells these technologies, but I have no idea about pricing.

Fabio


On Thu, 21 Feb 2002 09:15:38 -0700 Chuck Hards wrote:

Has anyone tried attaching a Peltier heat-pump to the back of a mirror, or
an array of them?  The heat produced by the "hot" side could be pulled away
by a rear-mounted fan blowing backwards, straight out of the tube.  The
"cold" side can get SO cold that it may be able to cool a mirror much faster
than a fan alone.  It doesn't address immediate boundary-layer problems on
the mirror's face, a small fan may still be needed if you're in a hurry, but
it may shorten appreciably the total cool-down time required.  I can tell by
recent posts that some people still aren't convinced that active cooling is
good insurance.

You know, you could even use one in an opposite configuration to heat an
eyepiece, kind of a high-tech "eyepiece cozy".
(Sticking your tongue to the flagpole in winter is nothing compared to
getting your eyeball stuck on a Plossl......just eliminating the "brain
freeze" is a step in the right direction!)

Just an idea, perhaps more practical than a "levitating secondary"!

C'mon, Richard, let's hear it.  Dig into this one!

Chuck