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iwols

obsy,to heat/dehumidify or not

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hi all obsy shed coming along nicely,base down shed down ror complete and pier setup and levelled,will leave heq5 mount in and some nights my ed80/ccd camera ect occasionally for security reasons,bearing in mind i have a gap of probably half inch down the underside of my ror,would you recommend heating the obsy or using a dehumidifier or do these just cause problems ,any thoughts appreciated,bearing in mind the british weather

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I find that keeping a fan blowing over my kit in my obsy, with a similar gap to yours, keeps all the  old metal surfaces dry. Without it they get condensation.

Hope the rest of the project goes well :)

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6 hours ago, iwols said:

Thanks Tim is that a cold blow

Yep. Moving air is less likely to condense it seems. I keep my scope and cameras set up in the observing room for weeks or months on end with no issues. I just have a small fan plugged in, and aim it up and under the scope cover.

I do heat my warm room, but only when I sit in there, but that has no impact on the observing section, except for when I open the door between them and the local seeing goes wild :p

 

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I also find that moving air fights off condensation. Heating or dehumidifying the whole observatory is an expensive solution when really you only need to keep the kit itself above the dewpoint. I'd put a large, loose cover over the lot and a very low output greenhouse heater or pet-warmer under that if you want to be double sure.

Olly

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I have a dehumidifier running in my obsy. I put a power meter on it a while back, and I seem to remember I worked out that it was costing me about 30p per day on the damp days (often in NW England). So not cheap as Olly says, although not the end of the world. It keeps the shed at 55% RH.

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2 hours ago, Chris-A said:

I have a dehumidifier running in my obsy. I put a power meter on it a while back, and I seem to remember I worked out that it was costing me about 30p per day on the damp days (often in NW England). So not cheap as Olly says, although not the end of the world. It keeps the shed at 55% RH.

I ummed and aahed about running a dehumidifier in my obs and finally decided that I didn't want to trust my electrics and optics to the vagaries of nature.  If you go down that route then you definitely need to cut down on the air flow.  I have a Pulsar dome and filled in the shutter and dome edge gaps with 7mm foam P-seal.  This cuts down the drafts but doesn’t inhibit movement of the dome or shutter.  I also got a Stego humidistat from RS, which allows much better control of the RH than the controller on the dehumidifier itself.  I set the RH at 60% and find that even when it’s foggy outside (worst case) the unit cuts in for two minutes every 15 to hold the RH at 55-65% (I monitor the environmentals with a little data logger and can see the rise and fall in RH).  On cold dry days during winter, it may go hours without running at all.  I think with control and draft exclusion measures it’s worth doing. The latter may be tricky with a ro-ro roof, I guess!

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I`ve a gap between the roof and walls with the roof overlapping by an inch this keeps everything at an even temperature and humidity. Des

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I don't have a heater nor humidifier in my observatory and I have never had condensation. I have an octagonal roof with a large uninterrupted gap all round giving excellent circulation of air inside. Get the air circulating correctly and you will have no need of heating nor humidifying.

Jim

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As described in the above two posts there is no substitute for a well ventilated set up.  I have never had a damp issue in my obsy thanks to the 30mm gap between the roll off roof and the sidewalls and the 150mm between the concrete base and the floor.  It makes me cringe when I see folks dropping the floor of their shed arrangement directly onto the cement base.  Cement takes decades to fully 'dry' and so is a constant source of moisture unless a decent air gap is maintained.

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Tried AC in the past.  For health issues I've not used or entered my obsy since last Sept but during the recent 'heatwave' did so to find the anti-condensation domestic fan still running and doing its job.  Fired-up SCT and all was well :hello2:

Nytecam

Edited by nytecam
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Really finding the useful advice in here. Will be building a obsy soon so am in the research mode right now.

My only question is, about this gap for ventilation between the roof and the side walls. Which image is the best representation of a good ventilated obsy? (Sorry not sure how to best explain what i wanted to ask so drew some majestic drawings using MS Paint)

vent1.jpg.0bbc44bbd4e115922e7a0e7f655a710b.jpg or vent2.jpg.c01fb8d8892f6a5862a385a18a63a83c.jpg

 

Thanks in advance

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Your top drawing is best - the second is wrong ie rain piddling down across the gap will cause leakage into interior.  Natural ventilation works when windy but when calm dew can occur internally and needs forced ventilation via a fan to mitigate. 

A small thermostatic  greenhouse heater under scope a further aid against dew on electronics in winter.

BTW using a dehumidifier really needs a sealed obsy [unlikely !]otherwise it will try and dry the whole planet's atmosphere drawn in through air gaps around doors and roof :hmh:

Nytecam - architect

Edited by nytecam
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1 hour ago, nytecam said:

Your top drawing is best - the second is wrong ie rain piddling down across the gap will cause leakage into interior.  Natural ventilation works when windy but when calm dew can occur internally and needs forced ventilation via a fan to mitigate. 

A small thermostatic  greenhouse heater under scope a further aid against dew on electronics in winter.

BTW using a dehumidifier really needs a sealed obsy [unlikely !]otherwise it will try and dry the whole planet's atmosphere drawn in through air gaps around doors and roof :hmh:

Nytecam - architect

Cheers mate, makes sense. That's what i thought but i wanted to be doubly sure

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For me it isn't about keeping the humidity at bay, a well designed shed/obsy will do that no problem.  The reason I have a dehumidifier is to remove the moisture after a session, when I close the roof and everything is now dripping.

Edited by RayD
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I have a heated “doggie blanket” which has an auto cut-off. Throw it over at the end of the session and it works well.

 

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