Quote:
Originally Posted by ZeroID
From what I've read if you are going to run a fan during observation you need some isolation to prevent vibrations in your optics. I'm going through the build and test myself with a 10" with a rear mounted fan so I'd be interested to hear of your results.
To what are you velcroing the fan ..?
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It's quite small and very light. It's velcroed directly on the glass by the center axis.
Quote:
Originally Posted by astronut
Marc,
I have a fan on my 12"LB. I let it run all night without any vibration or dew problems.
By heating it, you introduce another whole set of problems.
You would only heat a primary if you observed in extreme conditions (snow, ice)  |
Yeah John. Makes sense.
I have to admit I tried nichrome wire first in a spiral shape and as soon as I pumped some amps in there I could see the focus going south. Not good
Quote:
Originally Posted by bmitchell82
visual astronomy. no problems
astro photography problems.  |
Thanks Brendan. Might have to switch it off when imaging. Will test.
Quote:
Originally Posted by ballaratdragons
With my 12" dob I leave the fan running all night and have NEVER had a fogged up mirror. Even in frost and -6c temps.
The few times I have had my mirror fog up is when I forgot to turn on the fan.
It's not so much that the fan is cooling the mirror to prevent fogging, but that there is an airflow around the mirror.
Fogging will not occur when there is airflow.
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Ha... so you reckon I should take the fan further from the glass so I get air-flow around the cell? At the moment it's in contact with the back of the primary glass. I'll post a picture in a sec.