Re: [ATM] Re:Tees instead of triangles

[Mark Holm <mdholm@telerama.com>]

> I'm using this idea to address the thermal problem:
> 
> http://www.balinka.com/portfan.htm

You should really consider a front blowing fan.  With the 3 inch thick 
mirror, getting the air moving on both sides is going to help a lot. 
Also, perhaps even more important, a rear fan doesn't break up the 
thermal boundary layer on the front side that causes much of the image 
distortion.

Read

Alder, Alan, Thermal Management in Newtonian Reflectors, Sky & 
Telescope, Vol. 103, No. 1, January 2002, pages 132 - 136

Greer, Bryan, Understanding Thermal Behavior in Newtonian Reflectors, 
Sky & Telescope, Vol. 100, No. 3, September 2000, Pages 125 - 133

Greer, Bryan, Improving the Thermal Properties of Newtonian Reflectors - 
Part 1, Sky & Telescope, Vol. 107, No. 5, May 2004, Pages 128 - 132

Greer, Bryan, Improving the Thermal Properties of Newtonian Reflectors - 
Part 2, Sky & Telescope, Vol. 107, No. 6, June 2004, Pages ? - ?

Video examples from Bryan Greer's article are available at 
http://skyandtelescope.com/howto/scopes/article_1182_1.asp
or at
http://www.fpi-protostar.com/bgreer/may2004s%26t.htm This second link 
has more content than the one at S & T.

Alan, in particular gives a very graphic account of the improvement from 
a front blowing fan, even before the mirror has enough time to cool off. 
  While the mirror is still well away from thermal equilibrium, a front 
blowing fan gives significantly better images.

-- 
Mark Holm
mdholm@telerama.com

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