[ATM] 12V heating elements and Differential Dew Contoller - open cagetelescope

[Justin Modra <nitrohepcat@yahoo.com>]

How many watts are needed for a 10" primary (1" thick) and a 2.5" secondary in an open cage dobsonian? (using 330 Ohm resistors in parallel for all heating elements)
 
My dew heater is a differential dew controller by L. Haddix described at http://web.qx.net/lhaddix/dhcontrol.htm
However, this circuit is for Schmidt-Cass, not an open cage telescope.
In order to get this circuit to work, the scope heater LM335 had to be configured as a 3 wire sensor, not a two wire sensor (requiring the addition of another 5.1K resistor and 20K PC board pot). Also, compare the diagram to the specification sheets. I seem to remember a typo with respect to the voltage regulator.
 
Would it be best if the primary and secondary had separate heater sensors (individual controllers)? Or should the amount of heat applied to the optics be adjusted by using unique heating elements? (less wattage for the primary and secondary, more for accessories mounted to the outside of the optic tube)
 
I welcome any suggestions on implementing a differential dew controller on an open cage telescope. (and my observing location is VERY prone to dew and frost formation)
 
Regards,
Justin
 
 
 
 


		
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