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 mounted at the holder, eliminating the need for wires across the spider. Note: 9V rechargeable NiCd or NiMH batteries will not work, they are only 7.2-8.4V and have low capacity, rechargeable Lithium cells are 9V and will function properly. No more heat ropes! Three sizes to choose from.
Note: AstroSystems Dew Guard is designed to work with AstroSystems Newtonian Secondary Mirror Holders. If your secondary is glued to a centre post, the Dew Guard cannot be used. If your secondary is exposed and not inside a shroud the Dew Guard will not be effective in controlling dew.
An Optional Dew Guard installation kit contains all the hardware to wire the Dew Guard across the spider and connect to a remote switched battery box.