4" Dew Heater Wattage

[samtheeagle]

I'm in need of some help here...

I've just got a refractor, and am slowly learning the differences between it and my reflector. One of the biggest is that I'll have much more trouble with dewing. So I want to build a dew heater. I've done lot's of googling, and general reading around and I'm pretty happy with what I'm aiming for, with one exception... I've seen massivley differing opinions of what power the heater needs to run at. I've seen people say a mere 1 watt is fine and others suggesting 30 watts! Quite a difference.

Does anyone have experience in this area? I see that there are lots of home made systems discussed on the forums here, so hopefully someone knows

I'm looking for a suitable wattage for my 4" refractor...

Cheers.

[barkis]

I would have thought 3 watts would suffice to cope with that.

The formula to calculate Power is

W= V2/R if you want to make your own.

That reads, Voltage squared divided by Resistance.

So a supply of 12 volts across a load of 48 Ohms produces 3 Watts.

The Current in such an example would be 0.25 Amps.

Such an example would probably be useless applied to a large area like a 10 inch Newt. but should keep an ED80 clear of dew.

Of course it needs to be operational for a while, prior to viewing, or imaging, to give it time to do it's job. It won't be instantaneous, although I'm sure you understand that:D

Ron.

[samtheeagle]

Cheers Ron

I was picking 10W out of the air, but it sounds like I can trim that down a bit which is nice... I might go for 5W as a bit of extra oomph could come in handy. Then I'll regulate it in some manner, so that I can vary the output as the conditions require.