Hi Peter
I made a few DIY dew heaters for my telescopes using a voltage regulator, nichrome wire (encased in heatshrink). Works really well at a low price of well under $20.
I have a 3-d printer so printed a heat-shield to direct the heat down onto the mirror which also doubled as the surface I glued the nichrome wire to. Cardboard wrapped in packing tape would work as it never gets very hot when you get your resistances correct.
Not sure if I can post links to another forum, but here is what I did
https://www.cloudynights.com/topic/8...nd-controller/