This is a picture of the Dew Buster dew heater controller. Dew can quickly bring an end to an imaging session and the only real way to fight it is with a dew heater. I have dew heaters on my C6, the AT66ED and on the Telrad. The C6 uses an Astrozap dew shield with built in dew heater. The white cable on top of the Dew Buster is actually a temperature sensor which helps regulate the amount of power the Dew Buster applies to the heaters.