9V Dew Heaters - anyone using them?

[MortonH]

Came across these items. They use a 9V battery and simply strap on to your scope/finder/eyepiece depending on the size you buy.

No controller is required, and you can get by without a 12V power pack and long wires everywhere, although they also have a 12V DC input if you want to use them that way.

http://www.tech2000astronomy.com/zap/

For someone like me that likes to keep it simple these sound very useful.

Any thoughts?

[pdalek]

The numbers don't work out.
According to the Tech2000 website, the heaters have a power output of 0.5 to 5.29 Watts.
At 0.5W, a typical 9V battery will last about 6 hours.
At 5.29W you get 15 minutes (the Ah capacity at this current is about 1/2 of the normal Ah rating).

Maybe you could get by using one as a secondary mirror or finder heater. Anything larger, like a SCT, would require batteries by the bucketful.

[MortonH]

Yes, they're certainly not a replacement for a "normal" dew prevention system.