I had never 'had dew on the inside (ASI1600MM-Cool) since it is dried enclosed environment. But when the cooler hasn't much to do, then dew/ice could occur on the outside of the front window. My experience is that if the cooling is below maybe 5% capacity, the aluminum housing temperature get close to ambient. No heat is transported from the peltier element to the housing and then to the front mounted window. Ice (from humidity in the outside air) could form on the front side of the window since the very cold image chip is just behind the front window.
By putting the cooling on maximum (setpoint low) the housing get's pretty warm, heating the front window indirectly and the accumulated ice will disappear within minutes.
As long I keep the cooling above 10% maybe 15% capacity, ice or dew on the outside of the front window will not occur. The only problem is that you have to stay at least 30 degrees Celsius below ambient. So you will probably require different set of darks, bias and so on if the ambient temperature drops significantly. See attached graph I made of my ASI1600MM-Cool cooling:
Above 50% capacity, cooling is stalled and temperature will not drop but only more heat is produced.
