Hi all
David Pretorius was kind enough to make my 12" newt
cool. He built me an active cooling system, based on
Anthony's (bird's) design using peltier coolers with a cold plate and fans to extract the heat away. A piece of perspex, larger than the cooling plate, seals the back end of my scope.
The unit attaches to the back of my scope and is held in place using the
locking screws (not the collimation screws). It's powered by a normal computer case power supply (240v AC required, in this case).
I'm pretty sure Dave got the peltiers and required bits from one of the Dick Smith 12v travel fridge/coolers that you can use in your car.
The pictures below were taken on the first evening after fitting. The next day Anthony cleaned up some of the wires, and on the weekend I went and bought one of those spring loaded connectors that you see on the back of stereos/speakers. Once I fit that, it'll be a no-tools job to connect it and disconnect it. At the moment I need to use a screwdriver to plug in the wires that come from the power supply (the white ones you can see in the photos).
Well what can I say, it works perfectly!
Previously, on clear nights where the temperature dropped rapidly my mirror would never keep up with the dropping ambient and would remain 1.5-2 degrees above.
Now, I turn my cooler on and it easily keeps up with the ambient temperature, and will even cool to below ambient if I leave it running. I've only had it running a few times since coming home from Nambucca, but it seems to be able to cool about 3-4 deg an hour.
On one occassion, I took the scope out of the shed, ambient and mirror were both around 12deg just before it got dark. I had the cooler running for 2 hours and ambient had dropped to 5.7deg, and the mirror had cooled to 4.8deg.
I don't have it computer controlled like Anthony's yet - so it's still a manual turn on/off procedure, but if I want it semi-manual, then I canhook it up to a power-point timer and set the time(s) I want it to turn on and off based on previous experience, forecast min temps etc.
Anyway, thanks heaps to Dave P for building the cooler for me! And thanks to Anthony for his help in getting it running and the wire tidy up
And of course for leading the charge with active cooling!
Pics attached, taken from Nambucca Heads.
My 12" newt is now *cool*
