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condensation in obsy


nytecam

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I bought a Meaco DH8L junior dehumidifier, the desiccant type. Its on about 10 mins every hour on average although this can vary from being 10 mins every 2 hours or 30 mins every hour depending on outside conditions. Its automatic and does not run continuously unkess it needs too. After a session I put it on clothes drying mode which gets the obs to about 34% and produces a good breeze in the obs drying everything iut quickly. For ongoing maintenance usually around 50 to 60% dew to the mode I have it set to. A plus is it keeps the air warmer too, upto 10 degrees than outside so internally will never reach dew point temp unless roof open. Air circulation is very good when running.

Maybe running costs would be high I'm not entirely sure.

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That looks good :) Except for the price :D But I know high quality costs high price.

TBH I thought that was a good deal. Especially if it stops my kit from mould.

The low temp operation and constant drain are the key factors. The refrigerant ones are cheaper but freeze on cold night's.

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

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I have toyed with the idea of getting one of these - http://www.maplin.co.uk/mini-dehumidifier-617884

After the research I've been doing, my concern is regarding the low temperature capability of these type and their tendency to freeze up. They also become less effective at colder temperatures.

Here's a nice little summary on dehumidifier types and technologies:

http://www.ebacdirect.com/dehumidifier-types.php

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

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Here is the one I use http://www.maplin.co...t=Dehumidifiers just don't let the temp sink below zero, which it wont if you run one of these as it comes with a drain hose so you can have it on continuously. However I guess you could encounter a situation where the temp drops so much it goes below zero but then the unit will just not switch on until its warmer (it has built in safety). It is a desiccant type and will also provide heating some heating to the OBS as it raises the temp. Of course the X-dry above works in any temp and is only £50 more.

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Well it's arrived and is currently running.

As it's a ROR obsy I don't think it will be economical or realistic to run it all the time. The main aim is to run during the night for a few hours in the winter and after each session where the roof comes off.

I think the observing period is the main time of moisture introduction so a blast after any session will help.

It has a timer and remembers the settings after power off, so should start up off a timeclock.

Will report back when I have results.

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

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As it's a ROR obsy I don't think it will be economical or realistic to run it all the time. The main aim is to run during the night for a few hours in the winter and after each session where the roof comes off.

I think the observing period is the main time of moisture introduction so a blast after any session will help.

That sounds a good idea :) I often find everything dripping with wet from the dew after an imaging session.
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That sounds a good idea :) I often find everything dripping with wet from the dew after an imaging session.

Which I think then gets trapped inside and condenses on the cold surfaces. Typical though - I get the dehumidifier just as the air seems to be drying out!

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

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Well it's early days yet, but so far so good.

Last night was very cold, which is when the dew normally strikes on the SC primary. The dew heater strip cleared the corrector plate but there was no sign of any dew on the primary.

When packing away last night the inside of the obsy, the roof, the scopes, everything, were covered in a thick layer of frost. Before I closed up last, I banged the dehumidifier on for 4 hours and on inspection this morning, the obsy was as dry as a bone.

Will keep everyone posted.

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I think ventilation is the way to go. I don't suffer from condensation in the obs, all wood build with insulated warm room but no insulation in the scope section, but there are plenty of gaps around the roll off roof part, especially the drop down flap at the end which has a gap big enough for a cat to enter - judging by the coughed up fir ball I found on the floor the other day!

But after various disasters with my CCD I now encase it and the filter wheel (still on the scope) in a plastic bag with a 500g bag of dessicant in it and a velcro tie around the focusser.

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Just waded through the snow out to the observatory, not been out there for a few days, I was mildly suprised when I opened the inner door to find that it was not as cold as the warm room!! From the outside the dome looks like an igloo, inside looking over the top of the windshield there is a little light comming through the snow so no air in or out and all is dry as a bone, makes me wonder if I am doing right in looking at dismantling it all.

Jim

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I have an attic conversion starting first week of Feb, all the gear will be able to work from there, still a unsure at the moment. Once I have the attic up and running I will decide :).

Jim

You may find thermals from the house will affect the seeing...

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You may find thermals from the house will affect the seeing...

Will turn all the heating off an hour before I open up :D. To be honest I am not too worried about thermals, the observatory will be insulated from the house and the house itself is well insulated. I am not looking for Hubble quality seeing and as I am surrounded by houses in the garden I can't see the difference, no I will give it a try if it don't work out I will have converted the attic and still have the garden observatory which being out there again this morning it was bone dry and not a bit of dampness anywhere :)

Jim

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Well guys I think I'm between a rock or a hard place. I never got around to buying the solar vent but have been monitoring the moisture in the obsy since fitting the vents and the mount hasn't got condensated once. BUT after investing in one of these http://www.ebay.co.uk/itm/WHITE-SQUARE-DIAL-THERMOMETER-HYGROMETER-INDOOR-OUTDOOR-ANYWHERE-PLACE-OR-STICK-/310478626210?pt=UK_Kitchen_Accessories&hash=item4849f7dda2 it would appear the RH can get as high as 93% on a wet day. The odd thing is even my posters hanging on the obsy wall appear to have dried out also since installing vents ????

I'm still on the fence whether to invest in the solar vent as the vents are keeping the mount dry and the solar vent I'm assuming will have no impact on the RH during winter anyway.

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  • 2 months later...

I think this thread is dead now isn't it ? But for anyone who was interested ? Here's a quick update. Only one day have I found minimal condensation on the mount since fitting the air vents. I noted to my surprise this was on a reasonably warm and sunny day at the beginning of March. Although I didn't have the worst condensation problem in the world, when the mount did get condensation on it there would be a fair amount and now there is next to nothing. The RH may well get high but it sure isn't settling on the mount as often or as bad. I decided it was worth just keeping an eye out for a solar vent on the bay and as luck would have it 1 came up for a very reasonable £14 which I got fitted earlier today. I was shocked at just how quick these little 100mm fans run at. They do tend to slow a fair bit when hazy cloud passes over the sun but for the best part it continues to run. The fan can be turned off and the vent closed easily if necessary or left open as a simple static vent. I may not have a Paramount ME or a triplet APO but I value my kit all the same and given the results of just adding better ventilation to the obsy this has pretty much put my worries to rest if I'm honest. I'm sure a de-humidifier or heater would do a far better job at keeping the humidity down in the obsy but my objective was to make sure I did what I could to reduce the impact of condensation forming on my mount or scope. I kept within the budget I had in mind and I have avoided any electric bills in the process. I do want to point out again that I didn't have a terrible problem in the first place so if your finding each time you go in your obsy everything is drenched you may not get the same results I have but if your like me and would periodically find your mount dew ridden it might be worth considering better ventilation and air flow over your mount. I make particular mention to the mount as most obsy's have piers and I'm taking an uneducated guess that given piers are several feet in the ground and don't have things like damp course or anything this may well make them the coldest object in the obsy and so more susceptible to any warmer air condensating on it ????

post-8355-0-92114200-1364934508_thumb.jp

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I think this thread is dead now isn't it ? But for anyone who was interested ? Here's a quick update. Only one day have I found minimal condensation on the mount since fitting the air vents. I noted to my surprise this was on a reasonably warm and sunny day at the beginning of March. Although I didn't have the worst condensation problem in the world, when the mount did get condensation on it there would be a fair amount and now there is next to nothing. The RH may well get high but it sure isn't settling on the mount as often or as bad. I decided it was worth just keeping an eye out for a solar vent on the bay and as luck would have it 1 came up for a very reasonable £14 which I got fitted earlier today. I was shocked at just how quick these little 100mm fans run at. They do tend to slow a fair bit when hazy cloud passes over the sun but for the best part it continues to run. The fan can be turned off and the vent closed easily if necessary or left open as a simple static vent. I may not have a Paramount ME or a triplet APO but I value my kit all the same and given the results of just adding better ventilation to the obsy this has pretty much put my worries to rest if I'm honest. I'm sure a de-humidifier or heater would do a far better job at keeping the humidity down in the obsy but my objective was to make sure I did what I could to reduce the impact of condensation forming on my mount or scope. I kept within the budget I had in mind and I have avoided any electric bills in the process. I do want to point out again that I didn't have a terrible problem in the first place so if your finding each time you go in your obsy everything is drenched you may not get the same results I have but if your like me and would periodically find your mount dew ridden it might be worth considering better ventilation and air flow over your mount. I make particular mention to the mount as most obsy's have piers and I'm taking an uneducated guess that given piers are several feet in the ground and don't have things like damp course or anything this may well make them the coldest object in the obsy and so more susceptible to any warmer air condensating on it ????

Think you got yoursefl a bargain there - they usually seem to be around £40 whenever I've seen them on ebay. It looks quite large in the pic - what is it's diameter?

So far I haven't noticed any condensation in my recently completed observatory - early days yet though but I've thought about employing one of those solar powered vents should a problem occur. I'd like to avoid the cost of buying and running a dehumidifier if at all possible.

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