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Old 28-08-2016, 09:20 PM
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luka
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Join Date: Apr 2007
Location: Perth, Australia
Posts: 1,164
Haha, I knew you would like the E14 dual stage Peltier. Interestingly it is only 7W so it may not have enough capacity to get the heat out. Also the dual stage Peltiers are extremely inefficient... single stage has about 10% efficiency and dual stage then 1% efficiency.

Regarding the temperature, the colder the better. QHY8L (same sensor as us) goes down to -40C while QHY8-Pro goes down to -45C.

I have cooled 450D as well and, as you said, the noise plateaus around 5C. However, this is only part of the story:
  1. Canons do some heavy processing even on RAW files which probably explains why the noise plateaus. I believe Craig Stark had some excellent articles on this, I can find the links if you are interested.
  2. The ~5C plateau applies only for relatively short exposures. I tested it for 3 min exposures and the dark frames were identical to the bias frames at 2C exactly (for my camera/cold finger build).
  3. Going colder at 3 minutes exposure may not reduce the thermal noise but it definitely reduces the intensity of the hot/cold pixels.
  4. I recently tried doing 10 min exposures and things are very different compared to the 3 min exposures. At 10 min the noise definitely gets less when colder than 5C. There is still a significant noise even at -3C when compared to the bias files (-3C is my limit due to my insufficient power supply). I suppose that Canon's manipulation of the RAW files works differently for such long exposures.
Also I was unable to find any 20x20mm 12V Peltiers on ebay. Only ~3V and ~5V versions exist.

Few of the larger and possibly suitable 30x30mm Peltiers are here, here and here.
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