Dobsonian Mirror cooling

I got involved in a thread on CloudyNights about cooling mirrors. It started when someone had put their mirror in a water bath (half submerged!) as he had mistakenly let it get very warm during the day.

So there was a disucssion about whether water or air was better, the effect of blowing air, and finally the idea of blowing cooled air.

I jumped at the opportunity to do some real experiments. It turns out that blowing air on both sides of the mirror is about as effective as you are likely to get. The limiting factor then being the internal heat conductivity of the glass material. Here are some results.

graph

I hadnt really bothered much with fans on my 18”, but I’m installing them now!

Then the discussion got serious about active cooling. In some climates this might well be necessary. I've located a low cost Peltier cooling module and will be repeating the experiments when it arrives. Watch this space!

© AstroKeith 2021