ZWO ASI camera and dew problems, how to fix it?

Dew forming inside CMOS cameras can be a problem. Dew manifest itself by a nice dark oval in the center of the sensor, right where the cold finger is… A quick fix consist in asking the acquisition software to acquire very short exposures in loop mode. This has an effect of heating up the CMOS chip and dissipating surface dew. But, as mentionned, this is only a last ditch measure. I remain convinced that the real problem with zwo cameras is that the sensor housing is not airtight, which allows the desiccant

pellets to gorge themselves with humidity until they are saturated and can absorb no more. With my ASI6200MC, I find myself having to change the pellets once a year. On the picture above, you’ll notice there is a nice looking sensor window heater, but that works only for dew outside the sensor window. Changing the pellets when you don’t own a white room can be a pretty harrowing experience. Even though taking apart the front of the camera to gain access to the pellets is pretty simple, the hard part is not depositing dust directly on the sensor. To avoid that, I advise performing this operation outside (because our houses are dusty) at a time we pollen is low. I advise you buy brand new pellets from your favorite dealer as replacements. Some people stick the old pellets into the microwave oven for a few minutes to dry the old ones out. Either way, there is nothing worse in the middle of an imaging session than to have dew forming, so this is good maintenance. Nobody said the astrophotographer’s life was simple!