Observatory Humididty/Condensation

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Observatory Humididty/Condensation

Postby simon_d_street » Sat Dec 24, 2005 6:53 pm

Hi All,

Happy Christmas!

I'm just having an observatory installed. I am concerned about humidity/condensation. I can measure humidity and currently I keep my telescopes at between 50% to 70%. Are these reasable figures?

What dehumidifiers are used by of people, are there any models that people already use or can commend. Perhaps the concensus is not to bother?

Any help out there?

All the best

Simon
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RE: Observatory Humididty/Condensation

Postby Chanctonbury » Sat Dec 24, 2005 8:50 pm

Simon,

I thought I could get away without using a de-humidifier in my observatory dome but I was wrong! Luckily, I have one protecting my sports car so I quickly took that to the dome as having it in the garage was a bit overkill anyway!

There are a couple of things to keep in mind:-

1. You MUST get one that will work down to below 7 degrees C (most of the cheaper (B & Q, Homenase etc. ) ones don't. Remember, your observatory will probably get very cold in winter.

2. You MUST get one that has 'warm defrost' otherwise in very cold weather, the cooling coils will never defrost and you will simply build up frost until it stops extracting moisture.

I have an AQP (Air Quality Products Ltd) unit but sadly these are no longer made but there are others around. Assuming you are in the UK, try this company, their service is excellent:- SCES 023 9223 1300 ask for Brad Bull.


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RE: Observatory Humididty/Condensation

Postby simon_d_street » Sun Dec 25, 2005 3:43 pm

Steve,

Thats great. Can you quantify what is an acceptable level of humidity?

Many people with observatories don't seem to bother, but I'm sure this is not wise.

Thanks.

Simon
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RE: Observatory Humididty/Condensation

Postby Chanctonbury » Sun Dec 25, 2005 5:06 pm

Simon,

I cannot answer you question exactly - what I can tell you is that on the morning I discovered that I needed a de-humidifier I had water running off my counterbalance weights!!! What you need as a minimum is a level of humidity below that at which the heavy metal parts of your system have condensation on them!

Sorry to be vague but I just knew I didn't want condensation on my gear ....
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RE: Observatory Humididty/Condensation

Postby gammalog » Wed Jan 04, 2006 6:46 pm

Hi Simon

From what I've read, many times, it seems that the Fibreglass (GRP) construction observatory does tend to suffer from condensation problems. You don't say if this is the type of construction that you are having installed. In January 2002, I built a wooden construction 'Roll-off-Roof' observatory with an attached warm/control room. Both the observatory and warm room are well ventilated and each has a raised wooden floor.

My 10" LX200GPS has been permanently installed in the observatory for some four years now, during which time I have never experienced any dampness forming on the scope or anything esle. The warm room, which houses the computer equipment does have a thermostatically controlled heater, which is left on a 'Frost' setting throughout the winter months. However, the observatory area has no heater or any de-humidifier.

One major problem that I did have, was the amount of heat that built-up inside, during hot sunny days. To help with this, I installed a 6" extractor fan in the observatory and a smaller 4" one in the 'warm- room'. Both of these are thermostatically controlled and are set to switch the fans on when the inside temperature reaches 25 deg C.


Regards

Dave
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RE: Observatory Humididty/Condensation

Postby Chanctonbury » Wed Jan 04, 2006 11:13 pm

David,

I would expect a glass fibre dome like mine to suffer more from condensation than your wooden roll-off roof observatory and indeed, this seems to be the case. Interestingly enough ( actually it is a little sad! ) I monitor the dome temperature and humidity at all times. My dome is in the sun most of the day being located in a south facing garden and it remains cool inside even on the hottest of days - no doubt the bright white finish assists here as well!

There is, of course, a big difference in our gear that will effect the visible signs of moisture - the huge counterbalance weights on my equatorial mounts. They take in and release heat much more slowly than your equipment will.
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