Dew Heater Sizing for 6" Primary and Secondary?

After 2 very dewy nights at StarFest in Ontario this last weekend, I realize that I must finally make up some heaters for my 6" f6 (1" thick) primary and my 1.83" (1/2" thick) secondary mirrors!
The powder coated aluminum tube did little to slow down the dew, and, even though my mirrors are both recessed at least 4" from the ends of the tube, they both dewed up after several hours. Not a pretty sight, and the skies were great!
Kendrick uses 2 Watts Max. for that size secondary, and his 8" primary heater is about 20 Watts Max.
I plan to use small resistors glued to the backs of the mirrors in a distributed pattern.
I also plan to use small PWM controllers, or, I may make the Don Clement automatic feedback controllers, fed from 12 VDC batteries!
I am planning on mounting 17 of miniature 2W 0.47 Ohm resistors on the 6" primary and 4 of 15 Ohm 1 Watt resistors on the secondary!
Do these seem sized right? Any other advice?
Mike

Mike,
Here is a page that may be of help. They like 1/2 watt resistors. The page describes the making of heater strips but the info should still apply to your design.

http://www.dewbuster.com/heaters/heaters.html

Bob

I had a suggestion to use nichrome wire instead of resistors on the primary mirror. I did a test wind of some #24 wire on my old polishing tool, and by using a folded wire spiralling outward from the center, found that I can get about 10' of wire to fit nicely spaced. I found a supplier, on that auction site that shall not be named, that had 40' of suitable stuff that came to about $12 with shipping. It's a bit over 1 Ohm per foot, so it should work fine.
I do have to wind carefully to leave a space for the mirror mount supports!
I probably will use the 330 Ohm resistors for the secondary mirror, as per another suggestion!
Any other ideas?
You're doing great for me so far!
Mike.....>