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Fans blowing across mirror

Started by Ron777, 08/31/2003 07:52PM
Posted 08/31/2003 07:52PM Opening Post
Me again,

Can ya tell I'm getting in the mood to do mods to the scope? OK, I need flocking paper, and a light sheild off the end. But, how about fans, has anyone here done like they talked about in S&T and put fans blowing across the mirror on their scope? If so, how did it work? I'd be so nervous to cut holes in the new dob unless it was really beneficial.

Thanks,
Ron
Posted 08/31/2003 08:20PM #1
I tried two 4" fans blowing across the face of my 36" mirror. Didn't seem to help much. Then I added three fans blowing onto the back of the mirror and one fan blowing across the 11" secondary mirror. I also installed a dual temp thermometer, and can say that this setup definitely cools the optics down faster than without fans.
I think it really depends on how fast the temp drops where you are located and where you store your scope (house, garage).
Posted 08/31/2003 08:24PM #2
Ron,

I seem to remember you have a Guen Sheng type dob, is that correct? If not, I apologize for the diatribe.

If so, stop by and visit the skyquest-telescope yahoo group and do a search for fans.

We have come up with a very effective method of getting air across the primary and up the OTA without drilling any holes. I use 2 fans in a push/pull (or blow/suck if you prefer) set up behind the mirror with a "baffle" installed just above the primary. The baffle directs the air across the face of the primary. This configuration will put a tornado on your primary with 2 fans running at 12 volts. It blows gently and silently at 6 volts. I have verified that it eliminates all of the warm boundary layer air on the primary as well as any and all tube currents. All without any vibration showing up at the eyepiece. I was skeptical at first, but when I saw it first hand, I became a staunch supporter. Makes a difference at the eyepiece.

So stop by and cop a squat. We can help with the flocking as well.

Clear skies,

Tom
Posted 08/31/2003 09:08PM #3
Check
http://groups.yahoo.com/group/Dob-fans

David