insulating a telescope

[Kropster]

Thanks for the explanation m.tweedy.

The air is not such a good infra red trap as I thought......probably just as well, or the greenhouse effect would be disastrous!

[lrpingel]

Interesting article in the Sky at Night magazine that has just landed on this very subject. here is an extract regarding tackling dew "you can wrap the body of your telescope in shiny, low emissivity aluminium. central-heating radiator foil or an aluminised mylar space blanket is great for this job"

this is just part of several actions to combat the dreaded dew.

dont know if dew is your problem. the reverse i suspect but it is all about minimizing the temperature difference between the scope and the external environment.

Thanks for the info.  My problem will be  both avoiding heat and avoiding cooling.  Heat I think I can take care of with insulated building and air flow.  A fan on primary mirror makes sense and I think running ambient air through tube would also help to reach equilibrium with air temperature.  Of course running a fan blowing air into the tube will also blow dust and debris!  I'm starting with an 8" F6 telescope using conventional tube.  I think it would work better using a truss type construction instead.  Natural air circulation for all but primary mirror, the primary needs a fan or two at the back.  Low emissivity foil or white paint for primary box and secondary cage.  Any comments from those of you with much more experience than me?

[rfdesigner]

just found your comment after goggling for scope cooling as I'm treading the same path.

"Of course running a fan blowing air into the tube will also blow dust and debris!  I'm starting with an 8" F6 telescope using conventional tube.  I think it would work better using a truss type construction instead.  Natural air circulation for all but primary mirror, the primary needs a fan or two at the back.  Low emissivity foil or white paint for primary box and secondary cage.  Any comments from those of you with much more experience than me?"

"Dream telescopes" run their fans 24/7, but use a car air filter to remove all the dust and debris..   it also keeps spiders out!..  they don't like a breeze apparently, I'm planning on a blatant copy.

I'm also having a slight issue with the "metal cools down quicker" comment earlier in the thread.  Sure it feels cold to the touch as it's a good conductor of heat, but pick the right metal and crucially, with the right finish and it can be a supremely a poor radiator of heat which is really what we're interested in.

see:  http://www.engineeringtoolbox.com/emissivity-coefficients-d_447.html

Thus I am considering a vented tube with an aluminium foil finish to minimise temperature differences.

Derek

[Nillchill]

I am glad this topic has found some serious consideration from all respondents, I saw the sky at night article, and the thought of wrapping the scope in a metal foil somewhat perplexing merely for the fact that aluminium conducts heat far quicker,

so far I have found that a simple , thin low density foam wrapped about the scope to be the most efficient, couple that with a slow spinning fan behind the mirror pulling air  gently  "emphasis on the word gently" down the tube keeps the tube at ambient temperature. the idea being I am replacing heat lost to the atmosphere with heat from the atmosphere.

if anyone has tried something similar to this i would be interested to hear

once again thanks to all who have responded