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condensation in obsy


nytecam
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The roll off section of my home built obsy has a tin roof, which does attract droplets of water.

I checked up there today, and even though it hasn't stopped raining, the fan running the whole time blowing over my kit seems to have kept everything dry.

I think I am going to fit a solar powered fan at some point which will draw cool air in the rear of the obsy on sunny days and push out the warm air that builds up, it gets to over 35° in there some times in the summer.

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Not sure if anyone is interested but the single vent only went to reduce the condensation and not eliminate it. Doing a little research on the net I came to the conclusion I would need a vent in the roof to help circulate the warm air that was rising in to the dome of the obsy. This was done with a mushroom vent used on caravans to allow the air to escape from the roof while the lower vent now aids circulation of air around the pier and mount. I picked the mushroom vent up for £8.95 making the grand total £16. I will update to if this improves the problem any ?? Failing this I am considering using one of these to encourage air circulation even further http://www.ebay.co.u...=item4abf181765

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There's also the issue that water droplets contain spores. So when they condense onto a surface, there's the potential for mould to start growing on the wet surface. This happens a lot on painted surfaces or on anything that contains organic matter. Once that fungus starts to accumulate it can affect optical surfaces (camera lenses can get mould growing inside the barrel of the lens) and electronics, too. The problems can be corrosion as well as shorting-out components. Plus it smells bad.

I currently have a mouldy roof! I clean it down with a dilute bleach solution every few weeks. It appears in areas which remain damp - especially where glues have been used.

Condensation in my obsy is becoming a nuisance now. I've installed 2 passive vents to try to improve matters and have another to fit if needed.

I suppose insulation may help but the question is where? The floor is done, but do the walls and ceilings needs doing as well?

Typed by me on my fone, using fumms... Excuse eny speling errurs.

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I have had 4+ years of 'what moisture problem?' in my shed.

Optics, shiny metal and electronics have all been fine.

I have had a dehumidifier in there, but it has not had much to do.

The recent weather has been very different though.

There has been 95%+ humidity regularly indicated on my weather box.

In the last two weeks I have had to deal with two electronics problems.

The first was a goto handset that failed to boot.

Moisture inside was obvious.

Opening the case and giving it a bit of radiator time sorted that one.

The second was PC power supply that showed completely dead.

In this case opening and a quick heat through with a hair dryer got it going.

My short term solution will be to keep equipment powered more of the time and make more use of the dehumidifier.

In the long term, I will be watching this and other threads for ideas and suggestions.

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Some interesting and diverse opinions and options posted on this topic. I'm keeping a close eye on my obsy during these continuing rainy/damp conditions - small stream continues to run under raised obsy from next doors garden. :mad:

I'm coming to the conclusion that continuous forced AIR CIRCULATION, now for over a month, within my tiny obsy [except when in use] is the clue to keeping condensation at bay and as a backup I've a small electric greenhouse heater with thermostat immediately below the scopes main CB/'computer' just ticking over.

I've read somewhere that air circulation is orders of magnitude more effecting than heating in drying out an enclosure. Never had any problems under my big10ft domed obsy as a I suspect the air was never still or stagnant as it seems to be in my mini dome - we shall see :cool:

Edited by nytecam
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The natural way of venting mines and shafts, us to have openings at different heights. The difference in barometric pressures at the different openings causes a draft.

Don't think our obsys are that high to make this really viable but worth having low and high vents to encourage air movement through.

Typed by me on my fone, using fumms... Excuse eny speling errurs.

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My OBSY is nice and dry but was only built in the summer 2012, the walls are insulated with 25mm polystyrene and damp proof membrane, the roof and door are not insulated but I may do them in the summer.

The inner skin on the walls is recycled laminate flooring. The floor also has a damp proof membrane under laminate flooring.

I suspect I will install two vents also to circulate the air.

014.jpg

During construction.

010.jpg

Almost completed.

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I'm coming to the conclusion that continuous forced AIR CIRCULATION, now for over a month, within my tiny obsy [except when in use] is the clue to keeping condensation at bay and as a backup I've a small electric greenhouse heater with thermostat immediately below the scopes main CB/'computer' just ticking over.
I reckon the key to this is to direct the path of the air.

As Tim mentions in an earlier post, forcing dry air across the surface that dew condenses on and then expelling it will reduce the humidity inside the obsy. Just be careful not to draw moist air in, to replace the expelled air. No matter how much circulation we create if there are surfaces that are below the dew point, water will condense on them. If the air is warmed, the dew point of the air will be raised, but as soon as that air comes close to a cold surface, the air will be cooled again (until the surface warms up, from the warmth in the air and the energy released by condensation) and dew will form on it - or if it's absorbent, it'll just get damp.

Maybe a small infra-red heater would work if it was pointing at whatever you wanted to protect from dew? It would warm objects up without warming the air in between, so they'd be above the dew point.

Edited by pete_l
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Good idea, heating the objects you don't want to get wet. Also, you could put a piece of "sacrificial" cold material in there for water to condense on.

It a big iron rod poking out a hole in the floor - water condenses on it and rolls down the rod and out of the observatory (just a thought), or into a tray to catch the water.

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Hi Maurice,

I have tubular greenhouse heaters in my dome running from a hygrostat rather then a thermostat. The idea being to ease the dome temperature down gradually as the outside air plummets through the dew-point. I've been doing it for about 5 years and it seems to be quite effective. I used to have a lot of condensation inside the dome, with the resulting high humidity rusting buts, bolts, etc.

Supplementing the tubular heaters with a fan might be a good idea - I may give that a shot as seems like a low running cost solution.

Cheers,

Keith

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A quick update.

A quick update.

The caravan vent has reduced some of the condensation most notably on the pier and mount. (Never did have any major problems with the scope as this is covered with a motorcycle breathable cover) As this had shown an improvement I decided to go all out and get the van roof rotary vent (£40) which was fitted yesterday. Upon opening the obsy today I noted there was no drastic improvement over the caravan vent (£9). Given the rotary vent requires wind to actually gain any benefit over the fixed caravan vent I put it down to there wasn't a lot of wind during the night. BUT!! I did notice two dribbles of water on the motorcycle cover over the scope which then made me proceed to drowned the obsy with the hose pipe. For any of you considering the rotary vent..... don't bother there is a chance a fair bit of water on heavy rain falls will make its way on to your pride and joy.

Needless to say that has been returned for a refund and the caravan vent is back on. As the caravan vent has made an improvement I do want to pursue another avenue to see if I can improve on the fixed vent option. This has led me to considering using one of these

I will update as and when I have one in my possession but I am on the fence whether to splash for the battery back up model which allows up to almost 2hrs of darkness running on a full charge or just plum for the solar only version. Either way I am almost certain I will require a second lower vent in the obsy wall to allow in coming air to circulate the pier and mount better. My budget and intention is to keep the cost under that of a de-humidifier. While I have no doubt in the ideal world a de-humidifier is the best solution the obvious advantage if I can get a natural flow of air to control the moisture and temperature is that the ambience in the obsy should fingers crossed be better controlled and allow almost instant observing plus it's free.

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Another update of sorts. I'm currently flat broke after xmas so still waiting to get the readies together for the solar vent. I have been monitoring the condensation in the obsy and although I have no way of measuring the RH I have been paying attention to how condensated the greenhouse has been getting next to the obsy to get a better idea of which are the more moisture ridden days. There is no doubt the vents have made an improvement and although there appears a frosting for want of a better word there is no actual visible moisture on the mount. Before there were times when there would be beads of moisture all over the mount and most notably the counterweight bar and weights. Another advantage I was thinking with the solar vent is that it may also go to cooling the observatory in the summer where I have noted a +2° difference inside the observatory to outside meaning I actually had to wait for the scope to cool at times.

My only concern I have had with addition of the vents is I have noticed one or two little flies chilling in the tube. Some vents do come with fly screens so I may look to see if there is anything I can do to prevent any getting ideas about making the vent their permanent home. The flies are not so much the issue as the spiders and webs they attract. Any ideas on fly screens would be welcomed. I had considered using weed preventer fabric but feel this might be to dense and restrict the air flow I am looking to improve on.

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I got hold of some mosquitoe net from ebay and glued it to the back of the 2 vents in my obsy. I have not had any bugs at all since.

Jason.

Sent from my LT15i using Tapatalk 2

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.....I have no way of measuring the RH....

I have a little 'Weather Eye' indoor/outdoor weather station. The main display sits on a shelf indoors and a remote sensor is in the obsy. Which currently shows a temp of 7.3º C and RH of 89% in the obsy.... It was quite damp overnight!

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This is the mesh I used here: http://www.ebay.co.u...=item3375785d22

Jason.

Thanks Jason I'll look to get myself some :icon_salut:

I have a little 'Weather Eye' indoor/outdoor weather station. The main display sits on a shelf indoors and a remote sensor is in the obsy. Which currently shows a temp of 7.3º C and RH of 89% in the obsy.... It was quite damp overnight!

You might find this handy if your able to get RH & temp readings http://www.dpcalc.org/

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