HEATERSThe 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. Although I do not sell heaters all major Astronomy Retailers carry heaters such as Kendrick, AstroZap, and Dew-Not. These manufacturers have been making excellent heaters for years and DewBuster™ Controller owners have reported good results with all three. There are also other heaters manufacturers and most are compatible with the DewBuster™ Controller as well as the controllers made by Kendrick, AstroZap, and Dew-Not.
When 12V is applied continuously, the above mentioned heaters put out twice as much heat as needed in order to clear off dew that has already formed. A controller (such as the DewBuster™ Controller) is required to throttle the heat down to a level that will keep the optics slightly warmer than the air and also conserve battery power. Although they are categorized as "12V", they are intended to be used with a 12V Battery (which delivers 13.8V when fully charged) or a 13.8VDC Power Supply.
If you purchase a Power Supply make sure it puts out 13.8VDC and at least twice the Amps that you need. The Amps can be calculated by adding together the Amps for each of your heaters (usually listed on your heater manufacturer's web site, if not the table below gives the typical Amps) and also add the Amps for any other items running off the battery (telescope mount, accessories).
|Heater Size|||||Amps at Full Power|
|0.965" to 2"|||||0.2 A|
|3" to 4"|||||0.8 A|
|Hand Controller|||||0.8 A|
|5" to 8"|||||1.6 A|
WHAT HEATERS WILL I NEED?
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.
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.
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.