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Originally Posted by Bmanners
Bird: Your telescope looks brillant, I'm very impressed! How long did it take to build? Have you measured the hotside of the Peltiers? It looks like getting the heat out of the Al plate on the hotside will be a restriction in the heat flows. Peltiers can be great coolers but you HAVE to get the heat away from them VERY efficiently. This is where all those cheap powered eskies fall down. In a good system the hotside should be 5 to 10 C above ambient to get the most out of the peltiers.
Cheers
Brett
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I've just finished a new 13.1" scope, probably took about the equivalent of a couple of weeks work spread out over the last 6 months.
For the hot plate I was happy to use my hand to check that it wasn't getting too hot - I am running the peltiers at a duty cycle of around 75% so that they are on for 45 seconds and off for 15 seconds. I had made an error when I first wired it up, and the exhaust fans on the hot side were running off the peltier power, so they would switch off when the peltiers switched off. That wasn't too good as the residual heat would leak back through to the cold side, so I've changed it around and now the exhaust fans are running on an independent supply. The cooling curve is much better and the hot plate runs about 15 or 20 degrees above ambient, close enough for me.
The 3 peltiers together draw about 10 amps @ 12v, so there's an extra 120W of heat that I have to get rid of :-)
All in all I'm very happy with the combined mirror cell + cooler, it seems to be the best part of the new scope, the collimation adjusters are smooth and very precise as well.
regards, Bird