HEATERS
You may build your own heaters using these instructions: Building Home-made Heater Strips Or you may use any commercial heater strip which runs on 12V and has an RCA plug. Here are a few sources:  
MANUFACTURER WEB SITE NOTES
Dew-Not   Excellent heaters at a great price.
All are compatible.
Kendrick www.kendrickastro.com Premier and FireFly heaters are compatible.
Astrozap www.astrozap.com 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 it 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 where the 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 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.


Newtonian Reflector
You do NOT want to use a heater on the Primary Mirror because it needs to cool to air temperature to form sharp images. If your Primary Mirror is dewing up then you need a fan blowing on the back side of the Primary Mirror. If you do not have a fan mounted on the rear of the scope, then use a portable fan. On smaller Newtonians a dew shield can be made to extend the tube and shield the diagonal which will often prevent dew. On larger Newtonians it is usually neccessary 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 DewBusterâ„¢ Controller's Temperature Controlled Outputs and used with a Newtonian Temperature Sensor.


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