The Holey Scope

 This is the webpage for my 'holey scope'.  I have had this scope for years and it has always performed great when used visually, but I have never gotten decent lunar or planetary images.  After I got such good images from the 10" Orion a couple of months ago, I decided that the metal tube cooled faster and minimized tube currents.  This 8" has a sonotube with a couple of coats of paint and I decided it needed ventilation.  Thus the 'holey' scope was born.
This is a view of the main mirror.  It has 4 4" holes around it for ventilation and to allow tube currents out.
This is similar to the set up for side mounted fan cooling, but without the fan.  Since the scope is bound for NM and it is often breezy, this may well be front cooled. It is interesting to note that the holes are big enough to allow dust removal without moving the mirror.  No matter what direction the scope is pointing, there should be a hole available for rising heat to leave the tube. 



Below is a shot of the 'holey' OTA

 The 8" scope has a 1/10 wave University Optics mirror (F/6) with a 1/10 wave secondary.  I re-equipped it with a 2" Orion Crayford focuser with electric motor focusing.  I added an inside/outside thermometer to the tube to compare external and mirror temperatures.  A fan was added to cool the back of the mirror quickly.


 
 So it met its new 'first light last night (12/13/2010) with the Canon T1i attached.  I had purposely adjusted the new focuser so that it would at prime focus with the camera.  Unfortunately it then turned out that when a barlow is used one needs an extender. (You just cannot win).  So how did it perform?   I have a few pics posted from the session below.
One can see this might have problems with dew.  Since this will be in NM, that is unlikey to be a problem, but with the holes near the mirror, one could use a heat gun if necessary to remove dew.
Some are the full chip, some are 5x, some are 2x barlow at 5x on the camera.  I am pretty certain that these are the best pics I have obtained from any 8" scope. 

 
 
 
 
 
 

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