Newtonian reflector. Blowing towards or away from the mirror??
Cooling Fan
Started by JPorter, 12/22/2009 07:17PM
Posted 12/22/2009 07:17PM
Opening Post
Posted 12/22/2009 11:07PM
| Edited 12/23/2009 01:26AM
#2
Depends. Blowing towards the mirror will cool it the
fastest, if thats your main goal. However, if you've
got a solid tube, I've found it works pretty well to
have the fan blowing out at the bottom of the tube --
cold air enters the open top end, travels down the tube,
and is expelled by the fan at the bottom. Acts to suppress
rising warm air currents during observation.
fastest, if thats your main goal. However, if you've
got a solid tube, I've found it works pretty well to
have the fan blowing out at the bottom of the tube --
cold air enters the open top end, travels down the tube,
and is expelled by the fan at the bottom. Acts to suppress
rising warm air currents during observation.
Posted 12/23/2009 11:59AM
| Edited 12/23/2009 12:18PM
#3
The boundary layer directly in front of the primary and/or secondary mirror surface is the thermal effect you are battling. There are multiple variables that will determine the best solution for your setup (mirror thickness, telescope structure, and temperature variations at your locale).
Dual boundary layer cooling is employed through an array of holes on one side of the rocker box and fans pulling air across the mirror in Teeter designed dobsonian scopes. (see photo). Alan Adler recomends blowing air across the mirror in his January 2002 S&T article "Thermal management in Newtonian Reflectors". Bryan Greer mentions dew prevention as a side benefit of blowing air directly onto the primary, but that photograph showing a fan suspended in the shadow of the secondary directly above the primary with wire... 8O ... Scares me!
REFERENCES:
http://www.fpi-protostar.com/bgreer/fanselect.htm
http://www.pha.jhu.edu/~atolea/WAS/thermal_management_newtonians.pdf
http://www.teeterstelescopes.com/catalog.html
Dual boundary layer cooling is employed through an array of holes on one side of the rocker box and fans pulling air across the mirror in Teeter designed dobsonian scopes. (see photo). Alan Adler recomends blowing air across the mirror in his January 2002 S&T article "Thermal management in Newtonian Reflectors". Bryan Greer mentions dew prevention as a side benefit of blowing air directly onto the primary, but that photograph showing a fan suspended in the shadow of the secondary directly above the primary with wire... 8O ... Scares me!
REFERENCES:
http://www.fpi-protostar.com/bgreer/fanselect.htm
http://www.pha.jhu.edu/~atolea/WAS/thermal_management_newtonians.pdf
http://www.teeterstelescopes.com/catalog.html
Attached Image:
-Gary
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