[OICURMT]

Originally Posted by OICURMT! (From a different astronomy forum...)

Sky & Telescope had a DIY article back in about 2004-2005 (can't remember the exact year). Simple explanation of how it works. People are moving to nichrome wire with end resistors, but a resistor only based one is still a good way to go.

Everybody's Do-It-Yourself Dew Heater - Do It Yourself - SkyandTelescope.com

FYI Can't get cheaper than this...