AstroSystems Dew Guard secondary mirror heaters are for use on Newtonian secondary mirrors that are housed in a removable secondary mirror holder assembly. The mirrors are placed behind the secondary mirror, inside the holder assembly.
This heating system automatically senses the air temperature and the mirror temperature, then maintains the secondary at a preset (adjustable) temperature above the ambient air temperature. Gently warms the secondary at 2-4 watts when on full. The DG-1 has 4, The DG-2 has 6 and the DG-3 has 8 evenly spaced contact points for optimal thermal distribution. Uses any external 9-15 volt dc supply or you can run on a 9v battery mounted at the holder, eliminating the need for wires across the spider. These heaters have a dim red LED that will light up when the heater is operating.
These heaters save battery power as they only power up when they have to in order to maintain the programed temperature differential. They do not need a Kendrick controller to operate but if you do not like the idea of having a 9 volt battery hanging over your primary mirror then they can be powered from the dedicated 12 volt outputs of the DigiFire 7, Digifire 10 and Premier controllers. Cabling to accomplish this is available upon request.
Note: If your secondary is glued to a center post, the Dew Guard cannot be used.