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condensation in obsy


nytecam

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The wet and damp autumn caused havoc in my small domed obsy with scope power transformer blowing. Bought scope indoors for good dryout and now seems ok again with new power unit and ready to reinstall. Too heavy for me to lift so await my helpers arrival !

My condensation problems are in winter - I'm on clay and garden is sodden from Oct to April. Also at 1.2m depth there a very thin layer of sand and any puncturing of the this layer by neighbour's garden soakaways etc causes water to 'spring' to ground level and run my way :eek:

I had a small mains dehumidifier in my Meade dome a decade ago but it was ineffective as the space was not sealed and effectively it tried to dry-the-universe frown.gif Since used a small electric greenhouse heater with thermostat under the scope [when not observing!] but not entirely effective. Currently got a large but economic domestic mains fan running continuously and the constant air movement in the small obsy space seems effective - we will see. :cool:

How do you cope with condesation?

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I have a glass fibre domed observatory and suffer from condensation that that I resolve simply by using a desiccant/oven type de-humidifier which works really well even in the cold when a refrigerant type is no good.

I worried about de-humidifying West Sussex but I can help this with some material 'snakes' that my wife, Jane, made for me that fit in the gap between the dome overhang and the observatory wall. I get a 48%-52% reading at maximum humidity. My gear stays in perfect condition using this.

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I have never understood this need for de-humidifying - it always seemed to be the case that even a sealed dome, as soon as you want to use it, you lose any benefits by opening the roof.

what is the problem you are all solving ? Condensation on metal surfaces when the scope is tucked away ? Water on the inside of the roof , or something else ?

I have never really seen anything like this in my dome either during a long closed session or during a long observing session hence my confusion.

Then again my dome has a gale blowing through it as normal with all the 'ventilation' holes.

Cheers

Mike

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My dome sits above a brick shed so I don't have the same problems as you but there is certainly a fair bit of dampness in the atmosphere. I cover the mount and scope with a breathable, waterproof motorbike cover. I leave the mount switched on (motors off!) and have a small desk lamp with a low wattage energy saver bulb tucked underneath the cover. Initially I tried to make the dome airtight when not in use but soom gave up on this idea! My aim now is to leave it well ventilated and keep the mount and scope slightly warmer than the surrounding air. Haven't had any problems so far. I do tend to bring my cameras indoors though.

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The biggest cause of damp is actually standing air as the water vapour is then able to condense out on to surfaces that are colder than the air mass, this is why generaly it is exposed walls and metal structures that have the worst condensation issues.

De-humidifying the building is one way to control it, as would be small tube heaters, but for us that is not an effective solution, so the clear way to do this is AIRFLOW.

Install a small 100mm fan at low level (about 0.5m affl) and this will control all damp issues if you then ensure there is a vent at the highest point of the obsy. The easiest way to achive this is to cut a elongated hole and use a grill for a single airbrick from B&Q. The Fan does not need to be a fast model, in fact a 100mm 12V fan designed for a PC would be sufficient to meet the needs of the majority of small amateur enclosures. The fan can then be powered via a car battery that is trickle charged by a small solar panel, available from Maplin.

I would suggest that you do not use a 240V fan unless you are very sensible with the installation of electrical equipment and you can be 100% sure you meet the requirements of BS7671:2008 (Elec Regs) and can comply with the needs of Part P of the Building Regs (Yes I know that last one is dangly things)

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I agree about constantly moving the air in the obsy. I don't have condensation problems due to the climate here but I installed a self-propelled Whirlybird ventilator on the roof mostly to keep the hot summer time temps out of the structure.

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My RoR is of ali sheeting and where its not insulated inside I get quite a bit of condensation. Its far from well sealed, having quite a gap around the tracks and to the sides where the roof rolls past the main structure. At present there is no dehumidifier in the obsy but I will probably install a dessicant type at some stage.

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This is where the wood obs's win.. my pent obs is as dry as.. still I use a greenhouse bar heater from 9pm till 9am.

Try lining the floor in 5/8th T&G and line the roof & sides with sheets of thin polystyrene, my garage use to drip from the roof

until I lined the roof and steel door in polystyrene sheet.

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I seemed to get rid of the humidiry problem when I carpeted the floor. (Please don't think bad of me.. ) For £10 I got enough to put a double layer down and it works great. Not just for humidity, but as an extra layer of protection, should anything unseen fall.

My dome is on a concrete base, so EP's camera bits or anything else that might slip would have no chance otherwise.

Gordon.

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I have never understood this need for de-humidifying - it always seemed to be the case that even a sealed dome, as soon as you want to use it, you lose any benefits by opening the roof.

what is the problem you are all solving ? Condensation on metal surfaces when the scope is tucked away ? Water on the inside of the roof , or something else ?

I have never really seen anything like this in my dome either during a long closed session or during a long observing session hence my confusion.

Then again my dome has a gale blowing through it as normal with all the 'ventilation' holes.

Cheers

Mike

The problem is having electronic components dripping wet, I'd say.

Ventilation is a good idea but my observatiries are certainly well ventilated. However the steel (and and one synthetic) corrugated panel rooves do drip if not insulated.

A minimal heat source for putting under covers and under computers left out can be pet warmer pads. They are designed to be peed on by young mammals and so don't mind the damp!!

Olly

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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.

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I agree with the other threads as I have a dessicant dehumidifier in my Pulsar dome which has been running for over a year now; I generally keep it set to 40% RH but as it has been sub zero decided to leave it running in laundry mode so it keeps the obs a bit warmer.

If you have problems with condensation dripping of cold surfaces it is possible to buy an anti-condensation paint which is made from crushed volcanic rock, the paint is micro porous so when the condensation forms on the cold surface it "wicks" to the surface where it heats up and then evaporates. This type of paint can work 24/7 and provide an extra 4 degrees of protection 24/7; I recall it was developed by a chicken farmer in Norway or Sweden who had problems with condensation on the tin roof of his chicken sheds :laugh: but I think it is now used in the H&V industry on things that cannot be insulated such as chilled water pumps?

Anyway hope the above helps!

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Interestingly I have tried the same as you, a fan blowing over the kit constantly.

So far the air movement seems to have kept the it drier, and even helped dry off the frost after a night with the roof open.

I am considering having a gentle fan blowing upwards underneath my mount at the moment while imaging to see if that keeps any of the frost out of the obsy.

In the past I have used air blowing over a lens at a star party as an emergency dew preventer with good results too :)

Or we could all just move to Namibia..... ;)

Tim

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I think what this thread shows is that different solutions will suit different people and even different construction types.

As has been alluded to by a couple of posters, insulation of your floor is a crucial step to preventing condensation, it also helps keep your ruddy feet warm!

When we build Obsy's we always take into account the "comfort" of the telescope, understandably, but we often omit to consider such things as damp and the various causes of it.

Calculating the actual dew point is a complicated task, and not one for the faint hearted...so i have dug out a Humidity graph for everyone to save...(courtesy of Wikipeadia)

396px-Dewpoint-RH.svg.png

But if you want to calculate the dew point for your obsys or garden this very handy online calculator helps..

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After having some staff training on the principles of refridgeration and air conditioning, I was wondering if anybody has fitted a small air conditioning unit to their observatory.

A small system (demostic China made units cost from £150) would perform a couple of functions if a heatpump version was installed - cooling in summer, heating in winter and the air condition unit are very good dehumidifier?

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I'm currently having problems with condensation in a new shed with a tin roof. All of these tips are great, I didnt think to ask around here for help. Thanks guys. I can work off my turkey next week retrofitting some air vents for starters.

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A minimal heat source for putting under covers and under computers left out can be pet warmer pads. They are designed to be peed on by young mammals and so don't mind the damp!!

Olly

I've got a child's electric blanket wrapped round my scopes. It comes on for an hour a night to drive away any potential moisture and as Olly says, designed to be peed on!

I run it on a timeclock.

I also find opening the obsy door every few days, helps no end.

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

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This is a problem that has always befell my obsy and after reading this thread I decided to add some further ventilation to try and improve matters. The jury is still out on it's effectiveness as dew / damp / condensation over my mount and scope isn't a regular occurrence but none the less it was about time I gave something a try. I will update as it goes to whether this was a cheap and easy fix as it was a 1/2 job and cost no more than £7 but if it saves the ££££ of astro gear getting drowned every time the perspiration in the air is high then it will be money well spent. Thanks to the OP for reminding me to pull my finger out and getting the job done.

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