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Garethr

Constant damp weather

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Mm

Roll off roof. Until I got my dome my main experience of amateur observatories was the one belonging to my astro' club. This is in an open area and like the one above has ventilation around the edges of the rolling roof. It only got wet when we had it open all night on a dewy night.

Last night I spoke to a couple of dome owners but they both had domes with a clear gap around the rollers. My old style Pulsar does not. the gap is narrow and there is a skirt inside.

I was hoping to get input from old style Pulsar or similar observatory users. From all the pictures I have seen of similar, non appear to have added air vents. I would like to know if they have solved the same problem. And if they have whether any have added ventilation rather than going down the de-humidifier and heater route.

I will happily cut holes for ventilators in it if I know that they are going to work but don't want to butcher it for nothing.

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Two years ago!

In case anyone is currently having problems, an update.

I eventually put 'stick on' rubber insulation on the inside of the dome. This completely kills the worst condensation inside the dome and is usefully black. (if you are putting it on in cold weather, warm the fibreglass with a heat-gun before applying). I now happily leave books and charts out when previously they would have been damaged. Come to think of it I also leave a computer, a video camera and other electronic equipment out there now.

I use a good waterproof cover over the scope which already has a dust sheet on it. The dust sheet remains dry now (it used to feel damp even when there was no noticeable dampness elsewhere).

I also run an ordinary de-humidifier, with a tube to dispose of the water outside the observatory. It was the easiest first thing I did to control my problem. It may not work when it gets very cold but it does keep the observatory dry. I guess you get no condensation when all the water is frozen solid! It is possible that I could do away with this now I have the insulation, but I feel happier with it running when I am away.

On 'Sky at night' they say 'keep looking up' but 'keep yourself warm and dry' as well, and your equipment dry.

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Since somebody else bumped this :laugh2: I just thought I'd add that ventilation is fine for keeping your observatory dry when closed up, but after a full night of open-roof dew collection, I find it's an absolute must to run the dehumidifier in the scope side for a while after closing up.

But since I only have one dehumidifier, I can never decide whether to leave the warm room door open or not; I'd like to ensure there's no damp in there either, but probably shouldn't add warm air to the scope side? :icon_scratch:

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7 minutes ago, Shibby said:

But since I only have one dehumidifier, I can never decide whether to leave the warm room door open or not; I'd like to ensure there's no damp in there either, but probably shouldn't add warm air to the scope side? :icon_scratch:

Much debate about causes and cures for condensation (google 'workshop condensation')

But it's likely if you do that moisture from the warm, damp part will condense out on cold objects (e.g. the scope) in the other half.

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On 18/12/2015 at 21:23, Astroboffin said:

The whole point of no damp is loads of air circulation.....one day people will realise that ventilation is the key to NO damp....:)

Forget all the other thing like spending money on heaters or dehumidifiers it is a waste of money, just ventilate the room.....have a good constant airflow in and out.....and it will look after itself..

AB

Listen to what Astroboffin is saying here and you will save yourself a lot of time, effort and money. Ventilation to the point where you have free flowing air is key to a damp free environment. Heating and dehumidification are only required if you have constructed your observatory in such as way that you have eliminated completely or have restricted air flow. My observatory is single skin (cedar slats) no insulation or vapour barrier on the inside, with a 2 inch gap running the complete (circumference wall to roof).  The base is a wooden sub-frame mounted on a concrete base which has a damp proof membrane. It was built around 4 years ago now and suffers from no internal dampness whatsoever despite being unheated and with only natural ventilation. I think quite often in our eagerness to "boiler plate" the construction of our observatories we actually build in condensation and dampens problems. Keep it simple keep air flowing. 

Jim

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My ror wooden shed is really well ventilated. Air blows right through it around the roof and it’s made of single tongue and groove board that has a few gaps where the boards have shrunk. It’s got a fair few spiders which I always believes to like a dry house.  But I still get damp scopes and lens, tops of cupboards etc all wet.

Any tips?

 

 

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There's no one solution.

Ventilation is important, chiefly as a way of getting rid of moisture than preventing it collecting in the first place.

Ventilation with modest insulation (e.g. wooden shed type) can mean things stay cold in the morning and damp morning air gets in and drops dew on stuff that stayed dry all night.

Ventilation alone doesn't always work - otherwise things outside would never get dew on them.

A lot depends on your local micro-climate - e.g. does your obsy get warmed rapidly by morning sun, is it exposed to the wind, are you in frost hollow or river valley. Does it have a lot of thermal mass (e.g. brick) or not (e.g. fibreglass).

There are so many variables guidelines a can only be that for any structure like an obsy that has to combine being wide open to the elements with protecting things from high winds and heavy rain at other times.

Especially in the UK :icon_biggrin:

 

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27 minutes ago, Stub Mandrel said:

There's no one solution.

Ventilation is important, chiefly as a way of getting rid of moisture than preventing it collecting in the first place.

Ventilation with modest insulation (e.g. wooden shed type) can mean things stay cold in the morning and damp morning air gets in and drops dew on stuff that stayed dry all night.

Ventilation alone doesn't always work - otherwise things outside would never get dew on them.

A lot depends on your local micro-climate - e.g. does your obsy get warmed rapidly by morning sun, is it exposed to the wind, are you in frost hollow or river valley. Does it have a lot of thermal mass (e.g. brick) or not (e.g. fibreglass).

There are so many variables guidelines a can only be that for any structure like an obsy that has to combine being wide open to the elements with protecting things from high winds and heavy rain at other times.

Especially in the UK :icon_biggrin:

 

Great answer Neil thanks!  It's not insulated at all.  It's very much exposued to the sun all day, right from sunrise until a couple of hours before sunset where it disappears behind the house.  It's comprised entirely of wood, but sits on a large concrete base, and water can lie under the shed on the concrete.  I might invest in a dehumidifier to see if that helps.

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4 hours ago, tooth_dr said:

Great answer Neil thanks!  It's not insulated at all.  It's very much exposued to the sun all day, right from sunrise until a couple of hours before sunset where it disappears behind the house.  It's comprised entirely of wood, but sits on a large concrete base, and water can lie under the shed on the concrete.  I might invest in a dehumidifier to see if that helps.

If you have water pooling on the concrete ground slab then deal with that first; you may find that standing water from the slab is evaporating into the space above. I'd find out why the water is pooling on the slab and deal with that first.  Before installing a dehumidifier I would install a low level vent  - effective ventilation requires both high and low level vents to ensure adequate air circulation.  Your obsy sound very similar to mine in construction and as I said above I have no problems with dampness inside.  Now this does not mean I don't get condensation/dew forming on the equipment (scope/mount) when the roof is off - nothing you can do to stop that really. However the amount of air circulating when my roof is closed and the obsy secure ensures that moisture gets carried away. Good luck with whatever you chose to do.

 

Jim

 

Edited by saac
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Not managed to even make a suitable structure to cover my scope yet so still using a waterproof material cover, but would it help if you had a fan running to circulate the around around the obs. Even just a small desk fan?

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I live aside of a seven acre lake. Humidity is a big problem and to ensure I keep my Pulsar Dome and equipment dry. I have installed a desiccant dehumidifier with humidstat to keep the humidity below 60%. This keeps everything dry and fully usable on a day to day basis. Running costs? I just take 3 pints off of the amber nectar from my weekly quota :)

Steve

Edited by sloz1664

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I have the door to my obs open all the time that I am at home.  Get air blowing through and that fixes most issues.  Sometimes though, I concede, even that is not enough and the steel components are covered in condensation. I wipe down in that situation.

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I have a Pulsar 2.1m dome.  I have always run a desiccant dehumidifier in there, but at first was a bit concerned about the power it was eating. To cut down the considerable air ingress I fitted some foam draft excluder strip around the shutter edges and some foam 7mm p seal between the base of the dome and the top of the wall.  It filled the gaps, but not so much as to obstruct free movement of the dome and shutter. I also wired the humidifier to a Stego humidistat, rather than rely on the rather crude controller of the unit.  I have a little datalogger in the obbo and those measures were shown to have achieved a dramatic reduction in how much the dehumidifier was running.  Even on damp foggy nights, at worst it was tripping on 3-4 times an hour for around 3mins a run.  It has a 2 litre reservoir which I empty every 3-4 days in winter, when at worst it gets 2/3rds full (I did rig a drain up but was concerned about it freezing in winter). The obbo stays at a constant 60-65% rh and costs at worst a fiver a month in power. The dehumidifier also puts out enough heat to keep the obbo above zero on all but the most frosty nights.  I turn it off when I have the shutter open.  I can live with all that, for now, anyway.

Bottom line is, if you want to keep your kit and associated electrics dry, you might get lucky with Mother Nature, but you can’t beat some machinery if you are prepared to take the financial hit in kit and running costs.

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On 02/01/2016 at 14:09, Tinker1947 said:

On 02/01/2016 at 16:09, Gina said:

Arranging good ventillation without the rain blowing in is not easy.

I have been wondering about the spinning roof vents that you see on commercial vans etc.

Flettner-2000-Ventilator-for-Cargo-Vans-6050-600x600.jpg_cf.jpg.79dda1e635e50c19d2d63e61a21d0162.jpg

Edited by Stargazer33
Quoted wrong post!!!

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