Dehumidifiers in Observatories

[glend]

I have been running a small dehumidifier in my observatory during the last few days of rain we have had here, and it has really kept the obs nice and dry. The odd drip blown in past the side curtains has been evaporated away quickly, and judging by the half a litre of water collected from the air, it has to help protect the mount against corrosion. Highly recommend them. I got mine off ebay and it runs on 12V (comes with an AC adaptor as well).

[The_bluester]

What sort of power consumption is it Glen? I am a long way off my obs but have moisture issues elsewhere that a dehumidifier could be very useful for if the power consumption was not too high.

[glend]

Paul it says on it that its only 70 watts, the plug pack draws 1.5 Amps AC and outputs 12V at 6amps. Manufacturer is Ionmax

[marc4darkskies]

Been using one for years - wouldn't be without one!! I use this one:
http://www.dampsolutions.com.au/store/dehumidifiers/22L-Aquaria-Thermo-dehumidifier

You can get cheaper ones of course but you really need one that supports continuous mode (no emptying a reservoir) and one that turns itself back on after power outage.

PS: The one I have can also heat (maintains effectiveness if the temp drops below 2C). I have never bothered to use heating though - not cold enough were I am plus it's expensive to run. It's also a reasonably high capacity unit. Smaller ones work but can struggle after a wet night of observing.

[clive milne]

I rather like the look of the next generation smart air-con's from Samsung. They can pull 1L of water out of the air per hour and can be controlled remotely via wi-fi. There is an added benefit in that you could in theory have your telescope down to night time operating temperature as soon as you open the observatory which is the way professional observatories get around the issue of thermal mass inducing local seeing.
Being that they use inverter technology, the power consumption is 20% of the heat actually being removed by the head unit.

http://www.samsung.com/au/air-conditioning/wall-mounted-air-conditioners/F-AR09FSSSBWK1.html

[clive milne]

Another option worth considering is a PLC with built in Ai, Ao, Di & Do's.
They're cheap as chips these days and there are many sensors available which can be used to monitor pretty much any conceivable environmental or physical parameter. The outputs of course can include full PID analogue control and some of them have digital outputs with a high enough switching rate for PWM motor speed control if required.