Notes:

Source Voltage - chosen to be 12 VDC due to safety and remote availability.

Resistor Size - standard sizes readily available are 10, 15, 22, 33, 47, 68, 82, 100, 150, 180, 220, 270, 330,390, 470 ohms, etc.

Number of Resistors - 4 to 6 is a good number to work with around 1.25-inch barrel eyepieces. The necessary number will vary with your application.

Volts Per Resistor - in a series circuit, with each resistance the same, equal voltage is dropped across each resistance.

Resistor Power - should not exceed the wattage rating of the individual resistor. Typical ratings are 1/4, 1/2, 3/4, 1 watt, etc.

Loop Amperage - in a series circuit, the same current must flow through all component resistances in the circuit.

Total Loop Power - this is the total heating power of the loop. For best performance this value should fall at 2-3 watts, which should be sufficient to keep optics clear.