raurgo What can I do to get the sensor temperature to -10º? (the ambient temperature is 30º).
You cannot. The ASI2600 is only spec'ed to have a delta T of 35ºC.
Find a different manufacturer that uses the IMX571 sensor, if you need a larger delta T. There is a custom version of the QHY268M Pro that uses liquid cooling, for example.
There are two reasons to cool a camera, one reason is to obtain lower dark current ("thermal") noise, and the second reason, arguable much more important, is to maintain a constant temperature, so that dark current calibration files can work properly.
Furthermore, take a look at the dark current noise vs read noise of the ASI2600/ASI6200 series, and you will see that the dark current is very low compared to read noise for a 200 second exposure, even at 0ºC.
So, the key is to raise your target temperature to something like 0ºC when the ambient is at 30ºC, so that there is headroom for the cooler to operate. Otherwise, the cooler will, like you saw, reach 100%, and still not get to the target temperature: the cooler is therefore not be able to maintain a constant temperature.
I always back off the cooler target temperature when it gets above 90%.
Remember too that if you take a repeated sequence of short exposures, it will also heat the sensor up more than longer exposures, and you need to back the cooler off even more.
Chen
