ATM A Tube Full of Worms!!!

[Donn Starkey <dstarkey@solaris1.mysolution.com>]

I am mainly a lurker...trying to gleen bits of information which will help me in my 
quest for the perfect view.  I receintly purchased a C-14 orange tube.  The scope is 
permanently mounted on a pier in a wooden roll off roof ovservatory.  

I have been a little less than extatic with the views that I have gotten through it.  
Sometimes, mars is great.  At times, with a 7mm Neagler, I can clearly see the polar 
caps and and well defined dark regions.  Other times, I can see just the polar caps, and 
even then, they only appear as bright spots.  I also have a C-8.  On the same evenings, 
I seem to get better quality views through it.  I have cleaned the optics, and I have 
collimated the beast  but to no avail.  Lunar views are about as crisp as you can expect 
for an SC but the image seems to be plagued with heat waves...which I have attributed to 
thermals in the atmosphere in my view path.

Last night, I was changing from a barlow back to a straight eyepice.  Naturally the 
scope was out of focus and I had a view of the now familiar concrentic circles.  The 
circles were concrentic alright but the bright ring was moving...undulating is more 
like it.  After looking at it for a while, it looked like a bunch of glowing worms 
crawling around over each other.  

I assume that what I am seeing is air currents in the tube caused by a difference 
between the temperature of the scope body and the temperature of the air in the light 
path. I have followed the threads on ATM about mounting fans in the end of a dobsonian 
tube to cool the mirror.  One fellow even asked me to machine a fan inlet in the back of 
his C-14.  Is this what I need, a fan in my C-14?  I notice that the new Meades of 
comparable size to my C-14 have a fan mounted in the backplane of the scope so that the 
fan blows on the back of the mirror and the air exits on the other side of the backplane 
but still behind the mirror.  Would this bring the tube into temperature equalibrium 
more quickly?  Would I be better off to put a fan in the side of the tube so that I draw 
out the air inside the scope and replace it with air that is the same temp as the scope 
body?  What kind of filter would I need to make sure that I would not be drawing dirt 
particles into the scope tube to foul the mirror or the corrector plate? Surely someone 
has solved this problem before with a C-14 or similar scope.

Signed,

Tired of worms. 
-- 
Donn Starkey                       
e-mail: "dstarkey@solaris1.mysolution.com"
Star Technology, Inc.,  
Custom formulators of Epoxy, Urethane and UV Cure Adhesives and Sealants
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