Dew heaters

Pictured below of two examples of variations on the 2" eyepiece dew heater found on the previous page. The first is for a 1.25" eyepiece and is constructed the same way except that six 120 ohm resisters are soldered in parallel to form an array (=20 ohms) and then three of these arrays are soldered in series to give a total resistence of 60 ohms at 12v. A total of 2.4 watts is produced, enough to keep an eyepiece free from the effects of dew.

My version of the Kendrick Telrad heater splits the heat between two parallel resister arrays wired in series and held in place on both sides of the Telrad by the dew shield. At 2 watts per side my Telrad remains dew free even when the Kendrick controller is set on low. This is the same principle as the 2" eyepiece dew heater design except you are using two arrays and separating them by several inches(180 ohm resisters x 10 soldered in parallel = 18 ohms for each side that when both sides are soldered in series will = 36 ohms total at 12v ).