Dehumidifier

Kieran,
I think another solution I would suggest if you want to keep away from AC/mains power in your observatory, is to make provision for air circulation. If no air is circulating in a humid enclosure such as your wooden observatoy, then it will be an ideal breeding ground for mould and mildew. Try 2 (or 4) 12V fans, like what you have in a computer tower (they run forever, and take little in milliamps, and are quiet), and place them at opposite sides of your walls -> one side blowing in, the other blowing out. For added effect, place the inward ones at the bottom, and the outward ones at the top (ensuring withdrawl of any risen warm moist air).

I am currently working on this set up for my metal shed which suffers from condensation. Once I have all the gaps filled with expanded foam, I'll add the fans, and work them off of rechargeable batteries. The batteries will be recharged by day from solar cells. The circuit I am using is what you find in your cheap rechargeable solar powered garden lights.

Seanie.

Seanie --

Have you sealed the floor? (Is it on a concrete pad?)

I had a metal shed back in California, and even there condensation would drip off the underside of the roof in the winter. I solved most of it by sealing the concrete floor with an epoxy-based paint, but in the end had to move to a dehumidifier (I kept my mill and lathe out there, so it needed to be drier than you need for astronomy gear.)

Good luck with it,
-- Jeff.

Mate of mine has a white dome and he says that the roof was covered in condensation one morning and has had to stick in a dehumidifier.

I should really clarify, the scope has never been covered in dew, the inside of the upper dome is often wet but it makes no differance, its worst when its particularily cold while observing, so all you can do there is wipe it down with a towel if it bothers you, but I never do.

Seanie --

Have you sealed the floor? (Is it on a concrete pad?)

Hi Jeff,
thanks for the response. It is on a concrete pad which I poured myself. In hindsight, I should have put a damp proof barrier in it a few inches below the surface! As to the floor being sealed, It is in such a way that no running water/rain gets in under the timber beams I have it resting on (which in themselves are what's anchored into the concrete.

This is the shed: Argos online link .

There are many gaps throughout as a result of its quick erection facility (stop laughing...). What I need to do is fill in those gaps, best done with aerosol expanding foam - I reckon anyway. I had thought about painting the inside of the metal with a rubber (foam?) paint, but that kind of stuff is not available to Joe Soap in Ireland.

Either way, once I cure the condensation problem, it will next be sacraficed as a roll-off roof observatory candidate for me.

Seanie.

Seanie --

Without a vapor barrier, the concrete pad will wick up moisture from the ground underneath it, and it will then evaporate into the interior on warmer days. As soon as it cools at night, it condenses. This is more likely to be a problem than humidity coming in through cracks in the "erection". (In fact, I think the ventillation is probably actually helping -- I'd seal those as a last resort.)

I'd start by getting an after-the-fact seal on the slab -- either with a concrete sealer or epoxy floor-paint. The former is a lot cheaper, but I don't know how effective they are.

I like the rubber paint idea, though, as it will keep the metal from getting as cold, which will keep more of the water inside in the air (instead of condensing on the surface). They have spray-on stuff here for doing the back-sides of roofing slates, but I imagine that would make a tremendous mess.

Cheers,
-- Jeff.

Mate of mine has a white dome and he says that the roof was covered in condensation one morning and has had to stick in a dehumidifier.

I should really clarify, the scope has never been covered in dew, the inside of the upper dome is often wet but it makes no differance, its worst when its particularily cold while observing, so all you can do there is wipe it down with a towel if it bothers you, but I never do.

Dave --

My dome does that too. I've considered some type of insulative paint on the inside (perhaps like the rubber paint Seanie refers to), but I haven't bothered to do anything about it yet. I do have a de-humidifier in the downstairs part, and it never gets bad enough to drip on me (unlike my buddy Jerry's in South Carolina -- he used to think his leaked until he realized it was all coming from the inside!).

Cheers,
-- Jeff.

Hi Jeff,
I thought about somehow insulating the dome aswell to stop condensation, but then I was thinking that this would add weight to the thing and make it harder to move, and do you really want to thermally insulate the dome?, I think this would go against us when observing as we'd want the inside and outside termperatures to be the same, I think minimum cool down time is more important.

As for this rubber paint, where would you get it?, I'm trying to think of someway of preventing the base of the obsessionator getting into contact with the wet ground, short of using a plastic sheet.