[ATM] Re: ATM Digest, Vol 20, Issue 26

[OPTIXWIZ@aol.com]

Russell Jocoy's question on whether a fan blowing across the optical face of 
his telescope's primary mirror would affect image quality at the eyepiece is 
well taken.

Also, Mark Holm's advice and references are quite relevant.

However, Bryan Greer, Alan Adler's sometimes co-investigator, does not seem 
to grasp the virtually revolutionary significance of Alan Adler's 
anti-convection cell "forced ventilation." Adler's process work's virtually instantly. As 
soon as the fan reaches full speed, the full effect is seen at the eyepiece. 
There is no waiting for the primary mirror to reach thermal equilibrium with the 
air around it. Using Adler's process, the supposed resolution gap between 
good reflectors and good refractors is dramatically narrowed. Adler's own 
excellent 8-inch "home-built" Newtonian will make ANY 7-inch apo sweat!

Adler's process makes use not of laminar flow, but turbulent flow, which 
"sweeps" away the "thermal boundary layer" and convection cells surrounding the 
optical surface of the primary mirror. 

As Mark Holm notes, it is essential that the fan not impart perceptible 
vibration to the telescope. Alan Adler has researched this. My recollection is he 
has found that Sanyo muffin fans, the ones having ball bearing bearings, 
mounted with rubber damping feet against the telescope tube, performed very well.

Wishing you .99 Strehls,

Gene Cross
Fremont, CA USA
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