AstroSystems amazing Dew Guard secondary mirror 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 in a pinch. No more heat ropes!
