G'Day Mike,
Quote:
Originally Posted by okiscopey
My last observing session (Kulnura) was cut short by dew problems, so I've ordered one of those diddy little 12v hair dryers for the EPs and a dew-zapper from Bintel which fits on the front of my ETX125.
It seems these zappers need a controller, but they're a bit pricey.
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For under $40-$50 you can build your own:
http://www.iceinspace.com.au/index.p...63,285,0,0,1,0
Quote:
Originally Posted by okiscopey
As I already have a Jaycar digital thermometer which reads the temperature difference (to 0.1 deg. C) between two K-type thermocouples, so my cheapskate plan is just to keep an eye on the thermometer and simply switch the zapper off when temperature between the corrector and the night air is in the right range.
I'm not imaging, just doing general observing, and all of this is just the learning curve for hopefully bigger and better things.
Can anyone help with these questions:
1. Will this 'manual control' work reasonably well, or will the temperature swings be uncontrollable?
2. What is a workable temperature range? I understand if the corrector is the same or one or two degrees warmer than the air, dew won't form.
3. I only have a 7Ah battery but the zapper draws a couple of amps. Any guess as to the likely percentage of time it'll have to be on in Kulnura-type conditions?
4. How and where is the corrector sensor fixed?
Any links, comments or ideas will be gratefully received!
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I've never tried this sort of manual control, but I imagine it could get pretty frustrating. It requires a lot less power to keep the corrector warm so the dew doesn't form than to evaporate it after it has formed, just because of the latent heat of evaporation of water. Hence the value in the dew heater controller.
In terms of temperature range of a couple of degrees I suspect you could be right. While dew forms it also evaporates at the same time. Whether dew forms or not is just a balancing act between the two processes. If evaporation is dominant, no dew forms. If condensation is dominant, dew forms. Le Chatelier's principle. So you don't need must temperature difference to sway that balance. However, if you are manually controlling, and you let the dew form, it will the take a significant amount of power (or time) to clear the dew.
I would also recommend another battery to drive the dew heater. 7AH won't last you long.
Al.