HEATERS
The DewBuster™ Controller may be used with any commercial "12V" heater strip which has an RCA plug or you may build your own heaters using my Home-made Heater instructions. These types of heaters can not be run continuously or they will produce too much heat so they must be used with a controller such as the DewBuster™ Controller to regulate the amount of heat and reduce power consumption. Although they are categorized as "12V", they are intended to be used with a 13.8VDC Power Supply or 12V Battery (13.8V when fully charged). If used with a 12.0 VDC Power Supply they may not produce enough heat to prevent dew under all conditions. They should also not be used at more than 15 VDC as it could cause them to overheat and be damaged.

Although there are quite a few sources of commercial heaters, here are two that I can recommended based upon customer feedback :  
MANUFACTURERWEB SITENOTES
Dew-NotAll are compatible.
Kendrick All are compatible.

WHAT HEATERS WILL I NEED?


Schmidt-Cassegrain
You will always need a heater on the Corrector Plate and it should be placed around the main tube just BEHIND the Corrrector Plate Casting (NOT around the casting or the dew shield) so that heat enters the tube and warms the Corrector Plate from the inside. It is advisable to use a Temperature Sensor on the Corrector Plate Heater for best optical performance of the telescope. The eyepiece will need heat but I recommend putting the heater around the Star Diagonal because it will make it easier to change eyepieces and store heat warming the eyepiece faster. If you only use the finder for initial star alignment then you can just keep the caps on it, otherwise use a heater on the finder objective and a 0.965" heater on the eyepiece. If you have a guidescope, you can usually run its objective heater and eyepiece heater on a Medium Power output, but if you use it for observation then a Temperature Sensor on the objective will provide improved optical performance.


Refractor
You will need a heater on the Objective Lens and it should be placed around the main tube just BEHIND the dew shield so that heat enters the tube and warms the objective from the inside. It is advisable to use a Temperature Sensor on the Objective Lens Heater for best optical performance of the telescope. The eyepiece will also need heat, but I recommend putting the heater around the Star Diagonal because it will make it easier to change eyepieces and the Star Diagonal will store heat energy and when you change eyepieces it will warm the eyepiece faster. If you only use the finder for initial star alignment then you can just keep the dew caps on it, otherwise use a heater on the finder objective and a 0.965" heater on the eyepiece. A guidescope's objective heater can be run on a Medium Power output, but if a piggybacked scope is used for high-power observation then use a Temperature Sensor on the objective heater for best optical performance.


Newtonian Reflector
You do NOT want to use a heater on the Primary Mirror because it needs to cool to the air temperature to form sharp images. If your Primary Mirror is dewing up then install a fan blowing on the back side of the Primary Mirror to keep the mirror close to air temperature. If you do not wish to install a fan then use a portable fan behind the telescope blowing air at the mirror. On smaller Newtonians a dew shield can be made to extend the tube. This will shield the diagonal and is often enough to prevent dew. On larger Newtonians it is usually necessary to install a heater on the secondary mirror. If you have an AstroSystems DewGuard then it has a built in controller so it needs to be powered with steady 12V such as the 12V Output jack of the DewBuster™ Controller.  All other heaters should be powered from one of the DewBuster™ Controller's Temperature Controlled Outputs and used with a Newtonian Temperature Sensor.


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