Hi Paul,Tandy & D.Smiths have nothing relevant. A simple way to get the correct heat out of your nichrome wire, is to > connect one end to +ve, > then using a pair of pliers or a crocodile clip, starting at the other end, slowly slide the -ve wire down the nichrome until the desired temp. is reached... Taking into account the temp.diff. between inside your house/room & outside???? Bit iffy really!!! Then you have to insulate it somehow!! See original >
http://www3.sympatico.ca/mark.kaye/dewheat.htm
This might be worth a try >
http://www.dewbuster.com/heaters/heaters.html
I used an old electric blanket heater wire. If you cut a piece about 300 mm long, it will just be warm enough to keep your finderscope dry. I wrapped it round twice, (8 x 50 finder), & it works fine.
You will have 1 problem, ie; because it's resistance wire, you cannot solder it, but if you twist them together well & then solder, it works O.K. Sounds complicated but it's just fiddly. I used a small BP,(screw type), connector as security. You can also use a piece of 2 way terminal strip.
Mine runs all night no probs. Along with the E/Pc box heater & red LEDS. All up they total around 350 mA.
Hope the links are a help.
Regards, L.
ps. You need around 1.5 to 2 watts of heat to keep the dew off.
Ohms Law > I = E/R. E = IR. R = E/I. P = EI. E = P/I. I = P/E. I = current. E = voltage. R = resistance. P = Watts.
pps. ELLEX, what is a resistor? What is 'nichrome' wire?
Same thing, only packaged differently.
See 'Dewbusters' link. L.