Under clear sky, objects lose heat by radiation and cool down. If temperature drops below the dew point, air moisture will condense and the surface will fog over. With its high emission coeffizient, glass is prone to this kind of fogging, so eyepieces, which have no dew cap, sometimes show this effect within minutes.

A heater replaces the lost heat and prevents cooling and thus fogging. The difference of the temperatures is very low, so there are no problems with tube seeing.


Advantages of Kendrick dew heaters:

These heaters have been built to use only as much power as necessary and thereby not waste energy. One side of each heater strip is sponge-insulated. This directs the warmth of the heater element into the eyepieces, rather than being lost into the atmosphere, so that less energy is needed to keep your eyepieces moisture free.

Longevity is achieved through good design and workmanship. The insulation is turned around the edges of the heater, thus being protected against getting ripped off.

Moisture resistance is achieved by rubber sealing of the wires. No inner corrosion, no inner short circuits.

The Power connection consists of a cable with a male RCA plug and needs 12 V voltage. This ensures a hassle-free and very versatile connection to a multitude of controllers, as most manufacturers of dew-protecting heaters rely on the same basic specification. Nevertheless, the Kendrick system is especially comprehensive and the use of pulse width control saves energy.