This heater module has been designed specifically for use with an Allsky Camera system. The module affixes around the camera inside the clear dome and when powered, delivers a nice amount of heat to the inside of the dome, stopping it from fogging up on 'dewy' nights.
 The inner diameter of the module is 52mm, the outer is 72mm
The unit runs from a 12v DC source and current draw is at 12v  0.18A (2.1 Watts).

Please note you may receive a dew heater printed on a black circuit board. They are exactly the same specification as the green circuit board shown in the image.