View Full Version here: : Condensation in observatory
09-07-2010, 09:06 AM
Folks, I have a small problem with condensation forming in areas of my newly built observatory. Any ideas on how to resolve this? the buildings not leaking, and dries out real quick. so just a slight surface layer.
I currently have an air-gap between the rotating dome and obs. building that provises air flow, this seems to be helping keep the condensation down in the Wet Wellington climate. But might also be contributing to the problem.
Any recommendation on how to reduce the condensation would be very welcome. Just a tad concerned that theelectronics in the Mount might get damaged and or fungi could form on optics.
09-07-2010, 09:29 AM
Condensation is caused by the surface of your dome being cooled below the dew point of the air. Heating would solve it, but it's not a very good solution.
In normal buildings, this is why a vapour barrier is used (the shiny aluminium foil - sisalation). The sisalation keeps a sealed quantity of air between it and the roof so any condensation is minimised (no air movement to bring more moisture in), and condensation hopefully doesn't occur on the sisalation due the air gap insulating it from the cold roof.
If you have a slot type dome, you might be able to insulate the dome with foil backed insulation, but remember to seal the foil all around to make an effective vapour barrier, otherwise it could all end up a sodden mess.
I'm getting a little bit on condensation inside my POD this winter but I can't insulate inside as half the dome slides inside the other half, but at least the POD has a double skin, so the problem isn't bad.
09-07-2010, 09:33 AM
a fanhelps, plus i cover the gear with a BBQ cover
09-07-2010, 11:29 AM
They sound like good ideas so will look into insulating the dome and using a heated dog blanket around the peir and a scope cover. Long term the scope cover has to go as the observatory will be remote.
I think the main issue is the gap between the dome and the the walls. It lets a lot of air through, and given its wet here at present this could be the problem. Summer it'll be good, but winter, not so much. . A neoprene skirt would work well to close it me thinks. or maybe multiple skirts...
I'll look into insulation for the roof. Maybe a simple underfloor material would work?
The rest of the building is well sealed. Floor has moisture barrier, underside of floor has a molseal tar, topside is painted, exterior walls are painted and have a building moisture barrier on the inside. Then the internal side is lined with painted ply... so thinking that gap is the issue. Will post a pic soon.
09-07-2010, 12:12 PM
Run one of these between the hours of say 23:00 and 9:00. I have one and it works like a charm.
Also excellent after a night of observing when the inside of the dome is dripping wet!
09-07-2010, 12:26 PM
I had the same problem when I finished my obs. I fitted styrofoam sheets to the underside of the iron obs roof. It's not sealed along the edges, just cut to size and glued on, but no condensation has occurred since :)
09-07-2010, 08:14 PM
I had condensation in my observatory after a night of imaging but solved it now by getting a small column I'll heater which I turn on while I shut up the observatory. This in combination with a plastic barrier ( thick plastic ) underneath the foam flooring as well as the final step of covering all scopes and the mount with a large black plastic bin liner. It's important that the plastic cover is tied tightly with either a bunge cord or rope pull ties. No problems with condensation at all now on any of the equipment. I think just warming the air up at the last few minutes drives out most of my condensation/breath and that really helps.
As Houghy said a fan is good.
In my observatory I had a fan running 24/7 non stop, and also an extraction fan running non stop.
I bought fans from Trash and treasure markets, and the like.
Ran them till they dropped, and put in the next one, probably 6 each year.
A reasonable fan for $5.00 will run continuous for 3 months, no problems and they really do not add to the power bill
12-07-2010, 11:39 AM
Well I've managed to add another draft skirt to the obs. It's certainly cut down the condensation. It would appear that the moist outside air getting in between the rotating dome and the rest of the structure is the problem.
I'm leaving the dew heaters on 24x7 for now. It's just enough to help.
I have a telegizmo 365 scope cover so will use that for a few months, until I get it all sorted.
Tonights job is to install another draft skirt. this will give 3 skirts and 2 seals. Should still get a small draft, so this, fans and styrofoam sheets will probably fix it.
thanks all, I'll post some pix soon. We are getting there...
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