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Do I need dehumidifier / heater for winter in roll-off-roof observatory / damp climate with snow

Observatory
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Michael W. Dean avatar
Michael W. Dean avatar
Looking for info from people with experience from similar climates.   

Do I need a heater for dehumidifier in the winter for my gear when roof is shut and gear is not being used? I live rural North Eastern Oregon, US. It's damp but not as damp as Seattle / Portland. I'm far inland.

I'm looking for info about the longevity of the gear, not my comfort. I don't do visual astronomy and I control my gear from inside the house with ASIAIR. I'm usually only at the observatory to set up at the start of night and close up at the end of night.

It does snow here and is usually below freezing all winter. Observatory is thick poured concrete slab, with concrete block walls filled with concrete (solid concrete and rebar). Plus roll-off wooden roof covered with tin. I keep gear set up in there year round. 

Air can get in and out, but rain does not. I finished building it this summer, keep a dehumidifier in there, overflow tube comes out under the door. After rains a lot comes out. Dehumidifier won't work below 40 F (about 5 C), so should I turn it off for winter? Or do I need to run it with a small heater near it?

Concrete build means it's usually about 10 F warmer inside than outside, maybe more on sunny day. Anyone with experience on this: should I put a small heater in there and run the dehumidifier (and maybe a dew heater strip around the overflow tube, lol), or just turn the dehumidifier off for the winter. 

Thank you.
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John Hayes avatar
John Hayes avatar
Michael,
It is very unlikely that you need to do anything to protect your gear when the roof is closed.  Your gear will be at the same temperature as the inside air and unless the temperature of the inside air falls below the dew point, which will cause condensation, your gear will stay dry.  If the air in the building is typically 10F warmer than the outside, you are totally safe.  On top of that you live in a pretty dry region so you’ll never reach the dew point inside your building with the roof closed. 

Of course it’s a different story when you open the roof and you add radiative cooling to the sky.  I often rolled my gear in after a night out under the sky in Bend (where it is also quite dry) and it would be soaking wet.  So, be sure to use a good anti-dew system when the roof is open.

John
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Michael W. Dean avatar
Michael W. Dean avatar
John Hayes:
Michael,
It is very unlikely that you need to do anything to protect your gear when the roof is closed.  Your gear will be at the same temperature as the inside air and unless the temperature of the inside air falls below the dew point, which will cause condensation, your gear will stay dry.  If the air in the building is typically 10F warmer than the outside, you are totally safe.  On top of that you live in a pretty dry region so you’ll never reach the dew point inside your building with the roof closed. 
John

This is the answer I was hoping for and you know the area, living not that far away. 

Excellent, and thank you.
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Ruediger avatar
Ruediger avatar
Hi,

there are some criteria you should consider. e.g. glass fungus needs at least 17°C and more than 70% Hr to grow. If you brach these thresholds you should consider to do something against it. Also ventilating is important to avoid any form of fungus.

The low temp was also a challenge for me. Therefore I heat a little bit to be just above 5 degree C. But usually the colder it gets the less moisture you face, Therefore Hr is usually a topic when it is warmer.

You may also have a look on my setup and find some ideas concerning heating and dehumidifying: https://www.astrobin.com/1405hn/?nc=&nce=

CS
Rüdiger
Michael W. Dean avatar
Michael W. Dean avatar
Ruediger:
Hi,

there are some criteria you should consider. e.g. glass fungus needs at least 17°C and more than 70% Hr to grow. If you brach these thresholds you should consider to do something against it. Also ventilating is important to avoid any form of fungus.

The low temp was also a challenge for me. Therefore I heat a little bit to be just above 5 degree C. But usually the colder it gets the less moisture you face, Therefore Hr is usually a topic when it is warmer.

You may also have a look on my setup and find some ideas concerning heating and dehumidifying: https://www.astrobin.com/1405hn/?nc=&nce=

CS
Rüdiger

Thank you. 

I forgot about Lens fungus - Wikipedia.

I once returned a DSLR lens I bought on eBay because it had that. But it was an old lens, from the 70s or older. 

I will look at your link. 

Thank you.
Dale Penkala avatar
Dale Penkala avatar
I’m in mid-michigan (Auburn to be exact) and have similar conditions as you. I do not heat or dehumidify at all in my observatory. In the control room my laptop computers will shut down when it gets below about 40ºf I’ve found, so when I know its going to be on the cold side I’ll put my radiant heater on the very lowest setting so that it stays around the 50-55º range to eliminate that chance. 

Like others above mentioned air flow is a good thing and with the usual gaps in our buildings that helps that to happen but I do keep a box fan on low in the winter time and on high in the summer time. Also in the summer time as I can get the moisture and condensation it also helps to dry that off to help reduce the fungus issue @Ruediger is referring to. I built my observatory in 1999 and so far have not had any issues with fungus.

Dale
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Josh Jones avatar
Josh Jones avatar
I also live in North Eastern Oregon… pendleton.  I run a small nexDome and just run a dehumidifier 24/7….  when it's open it's the dew heaters keeping things under control.    But having a plastic shell, it can get frosty in my setup when it gets down to those really cold snaps… so I have a heat lamp I can engage when it's closed and it's really really cold.  A roll off roof may keep temps a little better.
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Michael W. Dean avatar
Michael W. Dean avatar
Josh Jones:
I also live in North Eastern Oregon... pendleton.  I run a small nexDome and just run a dehumidifier 24/7....  when it's open it's the dew heaters keeping things under control.    But having a plastic shell, it can get frosty in my setup when it gets down to those really cold snaps... so I have a heat lamp I can engage when it's closed and it's really really cold.  A roll off roof may keep temps a little better.

 
Thank you. Great info, and you probably have as close to exactly the same climate as me. I'm (on a farm outside) La Grande, Oregon. 

Heat lamp sounds like a good treatment. Thank you. 

Concrete is great thermally. Stays warmer than ambient in winter, cooler than ambient in summer. Is why they build houses out of it.

People told me "you can't build an observatory out of concrete, you'll get heat wave optical distortions through the night", but it's not true, and they were all parroting info, none was from experience

Also, with mine,  the sun goes behind the only near trees for the last 2 hours of the day. Also, it just doesn't make a difference.
Michael W. Dean avatar
Michael W. Dean avatar
Dale Penkala:
.... In the control room my laptop computers will shut down when it gets below about 40ºf I’ve found, so when I know its going to be on the cold side I’ll put my radiant heater on the very lowest setting so that it stays around the 50-55º range to eliminate that chance. 

...... I do keep a box fan on low in the winter time and on high in the summer time. Also in the summer time as I can get the moisture and condensation it also helps to dry that off to help reduce the fungus issue @Ruediger is referring to. I built my observatory in 1999 and so far have not had any issues with fungus.

Thank you Dale. Box fan sounds like a good idea. The guy who built the roof on mine was great. He didn't use any blueprints, just started building, but it closes evenly and fairly tight. When you're in it, you can see a little sunlight around the corner of the gaps, it lets in air but keeps out high wind. I've gone in it when wind is 25 to 35 mph and I feel it a tiny bit. 

So it has air circulation but a box fan will help. Excellent suggestion.
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Quinn Groessl avatar
Quinn Groessl avatar
Michael W. Dean:
People told me "you can't build an observatory out of concrete, you'll get heat wave optical distortions through the night", but it's not true, and they were all parroting info, none was from experience


That's the internet for you. I agree with others. Dew heaters and some air flow are key, and a small heater wouldn't hurt either.
Michael W. Dean avatar
Michael W. Dean avatar
Quinn Groessl:
Michael W. Dean:
People told me "you can't build an observatory out of concrete, you'll get heat wave optical distortions through the night", but it's not true, and they were all parroting info, none was from experience


That's the internet for you.

Yup. lol. The irony is that many very large professional observatories are housed in buildings made out of concrete. 

Any single-issue hobby is full of "nuggets of wisdom" that are false, and retold ad nauseum by noobs trying to sound smart.

Usually it's something someone believed without evidence, said off the cuff once, with authority, and maybe it was someone who was right on other things, so "of course that has to be true."

If someone says b.s. in a  confident enough tone, people who want to sound smart will repeat it.

Come to think of it, this is true outside of hobbies.
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