Having used my ASI120MM for a while for imaging the Sun, Moon and planets and having seen some excellent deep sky images taken with the camera I had a go with deep sky as well and obtained some reasonable results. But the one issue with the camera was it lack of cooling compared to dedicated deep sky imagers. Looking around the web I saw that a few people had solved the problem by simply adding a peltier and heat-sink to the backs of their cameras, so I thought I would give it a go as well and these are my results.
I bought a peltier refrigeration module from Amazon (
Experiment 1.
The smaller of the heat-sinks & fans were about the same size as the camera so I thought I would use those. However after mounting them on the back of the camera the cooling was not very good. Initially the temperature reported by the camera dropped about 5 degrees but after 10mins it had crept back up so I only had a 2 degree drop. The heat-sink was also very hot. Experiment 1 failure.
Experiment 2.
OK I still had the bigger heat-sink and fan, so the next I mounted these on the camera (using two of the four M4 threaded holes on the camera). Straight away there was a big difference, usually when the camera is started its temperature rises by around 5 degrees before reaching equilibrium. Now, with the fan and peltier off, the temperature didn’t rise. I assume that the heat-sink alone was helping to radiate the heat passively. I left the camera running for an hour for the temperature to stabilise taking 10sec images and it remained at about the same temperature all the time, then I turned on the peltier and fan. The temperature immediately started to drop and after 10-15 min it had stabilised at about 12 degrees below the previous value. I left things running for about 45min and the temperature remained stable over the whole time. Turning the peltier and fan off the temperature quickly increased back to near where it started. Experiment 2 success.
I did notice a small amount of condensation on the outside of the camera (none on the optical window), so I may add some insulation to try and prevent this. The dark current was significantly reduced, before the cooling was turned on the image pixel values had a minimum of 4, maximum 11516 and a mean of 136, with cooling these values dropped to 4, 4949 and 38.
Below are pictures of the cooler attached to the camera, a graph of the temperature (you can clearly see the period when the cooler was on) and a comparison of two 10sec dark frames both stretched by the same amount.
James
