A: In very humid conditions it is possible for moisture to condense on the OUTSIDE of a TEC camera optical window even though the window has a special warmer. Usually the moisture forms a round “spot” in the centre. This is because the TEC cooling can sometimes be too powerful for the front optical window heaters to catch up, and unequal temperature combined with high humidity can cause condensation.


1) A dew heater like the Altair RC or Split Newtonian heater to GENTLY heat the front face of the camera and this usually clears it. There is no need for excessive heat because it will impair the camera performance.

2) Slower or less aggressive TEC cooling can allow the small built-in heaters more time to keep up with the TEC cooling. Dewing is less likely if you cool the sensor less. In fact, with most CMOS sensors, cooling to below -10C does not really give any benefit in noise reduction after stacking – it just increases the risk of dew and more power being used, with more stress on the components.