[ATM] Conic Constant

[mdholm at telerama.com (Mark Holm)]

Probably much better to make the mirror accurate in a reasonably 
isothermal shop, then use forced ventilation to get it to equilibrium in 
use.  If it is warm enough to be badly off figure, it is undoubtably 
warm enough to cause thermal currents, and those are even worse than 
smooth figure errors.

The real pros, i.e. the ones building several meter class scopes, are 
all into serious ventilation.  Look at this picture of the Gemini North 
scope with it's dome open as for observing.  
http://www.gemini.edu/gallery/telescope/g0038.html

While we are at the Gemini web site, this picture showing the support 
system for polishing might be informative.  
http://www.gemini.edu/gallery/mirror/1885.html  Of course, those are 
active supports they are using.

Mark Holm