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Equipment Discussions >> Observatories

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MAURITS
scholastic sledgehammer


Reged: 09/22/09

Loc: Belgium
Dehumidifier new
      #6477638 - 04/20/14 04:28 PM

What is the best "dehumidifier" for observatory domes like the Pulsar dome or the SkyShed POD?

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JAT Observatory
NOT a Wimp
*****

Reged: 02/20/05

Loc: In the Primordial Soup
Re: Dehumidifier new [Re: MAURITS]
      #6477739 - 04/20/14 05:38 PM

I use an earlier version of this .

Mine has a latching power relay so it will work with remote controlled power strips and it works well in low temps without frizzing up. Since it also is an A/C unit I it to cool the OBS too.


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Lord Beowulf
Pooh-Bah
*****

Reged: 10/13/08

Loc: Cedar Park, TX
Re: Dehumidifier new [Re: JAT Observatory]
      #6477801 - 04/20/14 06:30 PM

Whatever you can find on Craig's List! I paid $50 for the nice hefty one you can see in the corner here. I bought it to use to help dry the polyurethane when I was painting, but given how tight the warm room is, I'll likely need it in the winter if I'm spending much time in there.

Beo




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MAURITS
scholastic sledgehammer


Reged: 09/22/09

Loc: Belgium
Re: Dehumidifier new [Re: Lord Beowulf]
      #6479529 - 04/21/14 04:54 PM

Is the dehumidifier permanent working in the observatory?

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TimN
Pooh-Bah


Reged: 04/20/08

Loc: Ontario, Canada
Re: Dehumidifier new [Re: MAURITS]
      #6479626 - 04/21/14 06:00 PM

Maurits, if you are thinking of getting a POD, I would also post your question to their yahoo group. Wayne (the owner) and the members are usually very helpful and should be able to help with your inquiry.

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Lord Beowulf
Pooh-Bah
*****

Reged: 10/13/08

Loc: Cedar Park, TX
Re: Dehumidifier new [Re: MAURITS]
      #6480344 - 04/22/14 12:34 AM

Quote:

Is the dehumidifier permanent working in the observatory?




I haven't needed it recently.

Beo


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Scott Busby
member


Reged: 03/04/12

Loc: Spotsylvania County, N. VA
Re: Dehumidifier new [Re: Lord Beowulf]
      #6480839 - 04/22/14 09:39 AM Attachment (17 downloads)

I use something like this. I run it constantly from Spring to Fall when I'm not in the observatory. Also has air conditioning. I vent the hot air out the bottom thru the observatory floor as well as the drain tube. My observatory is on a deck structure with a couple feet clearance underneath. In the winter when there is less humidity, I run a simple home depot oil space heater to keep the air a few degree above ambient.

Edited by Scott Busby (04/22/14 09:40 AM)


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TCW
Pooh-Bah


Reged: 11/05/13

Loc: The North 40
Re: Dehumidifier [Re: Scott Busby]
      #6481400 - 04/22/14 02:47 PM

My dehumidifier only runs when the humidity is above the set point. I am sure yours must be the same.

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MAURITS
scholastic sledgehammer


Reged: 09/22/09

Loc: Belgium
Re: Dehumidifier new [Re: TCW]
      #6481536 - 04/22/14 03:59 PM

Is there a specific type dehumidifier, that I need for an observatory (about 10 m) where sometimes the temperature is to hot or to colt?

There are so many different types, that I dont know what to buy ...


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TCW
Pooh-Bah


Reged: 11/05/13

Loc: The North 40
Re: Dehumidifier new [Re: MAURITS]
      #6481552 - 04/22/14 04:05 PM

A small observatory would likely call for a small dehumidifier. Some dehumidifiers are designed to work at lower temperatures. Check to see what their operating range is. You also will want one that has a hose attachment so it will drain outside otherwise it will stop working once the bucket fills up. If you have extremely high humidity a high capacity one might be your best choice.

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MAURITS
scholastic sledgehammer


Reged: 09/22/09

Loc: Belgium
Re: Dehumidifier new [Re: TCW]
      #6481561 - 04/22/14 04:12 PM

I see 3 different types:

Refrigerant dehumidifier
Desiccant dehumidifier
Peltier dehumidifier

What is than best to buy?

Is a "continue working system" a better choice?


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TCW
Pooh-Bah


Reged: 11/05/13

Loc: The North 40
Re: Dehumidifier new [Re: MAURITS]
      #6481622 - 04/22/14 04:46 PM

I would not use the desiccant unless your humidity levels are very low. You know your climate and conditions so match the capacity and working range of the dehumidifier to your needs.

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JAT Observatory
NOT a Wimp
*****

Reged: 02/20/05

Loc: In the Primordial Soup
Re: Dehumidifier new [Re: Scott Busby]
      #6481731 - 04/22/14 05:50 PM

Quote:

.... . I vent the hot air out the bottom thru the observatory floor as well as the drain tube. My observatory is on a deck structure with a couple feet clearance underneath.




Scott,
I am also on a deck. I vented my water and hot air out the side as I didn't want the moisture and hot air under the observatory.



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Lord Beowulf
Pooh-Bah
*****

Reged: 10/13/08

Loc: Cedar Park, TX
Re: Dehumidifier new [Re: JAT Observatory]
      #6484683 - 04/24/14 12:11 AM

Yes, you definitely wouldn't want to go with a desiccant unless you plan to be changing it all the time. That uses a chemical reaction (usually reversible) to pull water out of the air. The other two options are both similar, although I would suspect that a Peltier based solution is probably the less efficient of the two, although I could be wrong. Basically a refrigerant based system is just an air conditioner without the divider between "inside" and "outside". It pulls air in through the cooling (evaporator) coils, condensing the water on the coils. It then runs that cold air through the heating (condenser) coils, bringing it back up to something above room temperature. This is generally pretty efficient since the cold air is being used to cool the hot coils that are making the refrigerant to cool the cold coils! However, the whole process takes energy and that energy ends up as heat that is exhausted as the warm air out of the unit. The result will be that all the energy used to run the unit goes into heating up your room. That's fine in the winter, but for the summer months an air conditioner has the advantage of cooling the room as well as pulling the water out of the air. It just doesn't do it as efficiently since it's using hot air (outside air) to cool the condenser coils.

Beo


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DeepSpacBlakHole
member


Reged: 04/07/14

Re: Dehumidifier new [Re: Lord Beowulf]
      #6484769 - 04/24/14 01:24 AM

Single hose AC's just suck air in from the outside (through every crack) to replace the air being blown outside.. Inside air has to be used to cool the compressor. This causes a pressure difference from inside to outside.. Very inefficient. The humidity/temp will never be that far away from the outside humidity/temp.

You need a dual hose ac that has a separate hose for intake to cool the compressor.

Edited by DeepSpacBlakHole (04/24/14 01:28 AM)


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ManicSponge
sage


Reged: 11/29/13

Loc: Wenatchee, Wa.
Re: Dehumidifier new [Re: DeepSpacBlakHole]
      #6485370 - 04/24/14 11:25 AM

Be aware that any of the compressor based units (which are the only ones that work well) have a large starting load. They can give a pretty good voltage drop to the circuit they are on, at start up.
If you have sensitive equipment plugged into the same circuit, it might be a factor worth considering.
The compressor models also add significant heat to a small area, sometimes requiring AC to offset it.
I would skip the Peltier units.
http://secretscotland.wordpress.com/2013/09/13/the-useless-world-of-the-pelti...
We bought one to try in our travel trailer. I was skeptical, so I left the bathroom vent fan off when I took my shower, and set the unit in the room when I was done. I came back 3 hours later, and there was not a drop of water in the bucket.
Regards, Kyle

Edited by ManicSponge (04/24/14 11:29 AM)


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Midnight Dan
Postmaster
*****

Reged: 01/23/08

Loc: Hilton, NY, Yellow Zone (Bortl...
Re: Dehumidifier new [Re: MAURITS]
      #6485422 - 04/24/14 11:48 AM

Quote:

I see 3 different types:

Refrigerant dehumidifier
Desiccant dehumidifier
Peltier dehumidifier




There's a 4th type - basically a low power heater/fan.

Keep in mind that condensation only occurs when the combination of air temperature and relative humidity puts it below the dew point. There's 2 ways to avoid that: 1) keep the air dry with a dehumidifier, or 2) keep the air temperature warmer than the dew point. Warming the air a small amount and circulating it with a fan will keep it, and the surfaces in your small observatory, above the dew point and dry, without the power consumption and drainage issues that go along with a dehumidifier.

I know of a couple of people who have had good success with these units from West Marine in their PODS.
http://www.westmarine.com/west-marine--air-dryer-with-fan-dehumidifier--P0078...
They produce a nice low 100 watts of warm air, and are designed to run continuously to keep a boat cabin dry for long periods of time while the boat is at dock.

I purchased one but can't use it because my solar power setup doesn't provide enough power to run it for very long. I may run 120v ac out to my POD at some point and then I will begin using it.

-Dan


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DeepSpacBlakHole
member


Reged: 04/07/14

Re: Dehumidifier new [Re: Midnight Dan]
      #6485617 - 04/24/14 01:31 PM

Wouldn't increasing the dew point still leave you vulnerable to mold on your optics? Or Mold in general? I don't think mold cares about the temp as long as theres enough moisture in the air? Thoughts?

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Midnight Dan
Postmaster
*****

Reged: 01/23/08

Loc: Hilton, NY, Yellow Zone (Bortl...
Re: Dehumidifier new [Re: DeepSpacBlakHole]
      #6485843 - 04/24/14 03:13 PM

As far as I'm aware, mold needs moisture to grow. As long as things are dry it shouldn't be a problem. Humidity in the air is just that - in the air - not on surfaces or available to organisms, unless it condenses. Could be wrong, but I thought that's the way it works.

-Dan


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MAURITS
scholastic sledgehammer


Reged: 09/22/09

Loc: Belgium
Re: Dehumidifier new [Re: Midnight Dan]
      #6487134 - 04/25/14 04:38 AM

Quote:

Quote:

I see 3 different types:

Refrigerant dehumidifier
Desiccant dehumidifier
Peltier dehumidifier




There's a 4th type - basically a low power heater/fan.


-Dan




I think this is the way that I go, with the low power heater/fan!

It's the ideal solution for the small observatory ...


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