Kenrick Dew-Guard 1 - Electronic Secondary Mirror Heater
A 6' patch cord is supplied with each heater so that power may be supplied from the controller if the controller is mounted farther down your scope.
The Dew-Guard heaters have temperature sensors built in and are self regulating.
FURTHER INFORMATION ON THE Dew-Guard HEATERS
The Dew-Guard heaters are a temperature controlled heating system designed to help prevent dew formation on a telescope's secondary mirror. The uniform distribution and controlled heating avoids air currents and optical distortion.
INSTALLATION OF DEW-GUARD HEATERS
Note: The indicator LED will only light when the temperature conditions activate the Dew-Guard. The LED will not light when power is applied if the secondary mirror is above the air temperature.
The Dew-Guard senses both the ambient temperature and the glass temperature using two sensors: one on the circuit board and one on the pigtail. It compares these and applies power to the heaters when the glass to air-difference is less than or equal to the preset value. A small LED indicates power consumption and is at "half" brightness when there is a 2 degree or smaller difference between the air and glass. The adjustable potentiometer is preset at the factory with heat being applied when the secondary mirror is still 1-3 degrees C above air temperature. A small screwdriver can be used if adjustment is necessary.
Using a small temperature difference preset will cause the unit to turn on sooner and may be used for the most severe conditions. A large temperature difference preset will allow the mirror to nearly reach air temperature before turning on, the preferred setting for typical dew or frost conditions. This will give the longest battery life and have a negligible effect on the optical figure of the secondary mirror while avoiding tube currents. The unit will remain off until the secondary mirror reaches the preset air/glass setting, then cycles on and off as the secondary mirror is gently heated.