Tuesday, October 8, 2013

ASI 120MC and Peltier--An Experiment

The ASI 120MC is a truly flexible camera. It can do planetary imaging as well as deep sky. However, like all uncooled cameras, it produces significant amounts of noise. While dark frame subtraction can take care of much of this noise, cooling the chip can greatly reduce noise and minimize processing. It also makes it easier to see deep sky objects as you monitor the exposure.

The camera's metallic case is a good conductor, so I decided to experiment to see how much cooling I could get by surface mounting a peltier cooler. I bought a very inexpensive (less than $5) 93-watt peltier and a $15 PC heatsink and fan.

The Alpine 64 has low vibration and 90 watts of cooling capacity

I then mounted the peltier to the heatsink (the heatsink has a conveneint adhesive thermal pad).

The peltier mounted on the heatsink
All that remained was to add a 12v power supply, place it on the imager, and turn the contraption on!

The working device!
The results are very interesting. The following images are captures showing chip temperature and the resultant image noise for a 17-second dark field exposure (click for a full-size image where all the noise will be visible).

Initial image. The original chip temp was 22 C. In a few seconds, it had cooled to this value.
The final image was taken at 0.5 C, about 5 minutes after turning the device on. As you can see, the noise is much reduced.
Significant noise reduction at 0.5C
However, the peltier and fan proved a little too demanding for my 13.8v, 6 amp supply (I knew I was pushing it) and it died rather horribly before I could continue cooling any further. However, the experiment was a success. The heatskink will be attached to the imager with rubber bands or bungies and powered with a more capable supply (like a car battery). For less than $25, this mod makes deep sky imaging a little easier for this fine camera. I appreciate very much the websites and forums that helped make this project possible.