Re: [ATM] Forced Ventilation

[Rick M <starman_962@yahoo.ca>]

Hello Doug;
       I have had a fan on my dob for awhile now
drawing air down the tube and out the back which is
closed except for the fan.
 I have found it to be a great help in cooling down
the primary during summer because my telescope is
stored inside my baby barn and the heat in there can
be vastly higher then the outside air, have never used
it in the winter time.
 Although my mirror is a 10 inch by 7/8th plate glass
the fan really shortens the cool down time.
I have yet to notice any vibrations with it,even
though it is solidly mounted to the back but that does
not mean there is none, will check more carefully next
time I use it just to be sure.
Can you explain how you dampened your fan?

I for one can not see how blowing air up the tube
would be a good idea though I have heard tell of it,
you would think this would create even more turbulance
in the tube, main reason why I did not try it though
for all I know it could be a much better way of doing
it,anyone have an opinion on this?.
  
   Only drawbacks I have found is that once you start
using the fan you can not turn it off or things get
real turbulant, plus the odd times when I almost see
two objects when looking through the eyepiece but this
only happens if I rush the cooldown and try observing
a bit to early, have never noticed this effect at any
othertime so I figure and hopefully correctly that
this is the problem.

====
Rick M
my astronomy & atm site
http://www.geocities.com/starman_962 

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