From: Mark Holm 
To: atm{at}shore.net
Reply-To: Mark Holm 


Consider very strongly putting in a fan blowing across the face of the
mirror, with vent holes or a suction fan opposite (if the tube isn't open).
 Very good evidence presented in two Sky & Telescope articles shows
this will almost certainly help get the best out of this mirror.  A light
metal tube will probably have fairly high resonant frequencies and low
damping.  This makes it a
bit more likely that vibration from the fan(s) will be a problem, but there
are ways to deal with that.  (I think I read on this list that plain
bearing computer fans run smoother than the ball bearing ones.  Panasonic,
I think, advertises computer cooling fans with a special plain bearing
design they call "HydroWave".  Supposed to be very quiet
(smooth).)

Mark Holm
mdholm{at}telerama.com

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