Dealing with cold and damp in the observatory

[Penguin]

I am looking to protect the gear I have in the roll-away Tardis observatory I built this year (see this thread on the build if you are interested:

A dehumidifier: https://www.appliancesdirect.co.uk/p/md400/electriq-md400-dehumidifier)

A greenhouse heater: https://www.greenhousepeople.co.uk/products/3872/slimline-eco-heater-55w-tube-heater-with-thermostat/

The observatory itself is around 1 meter square and 2 meters tall. Ventilation is currently provided by the gap in the base around the pillar, a large vent behind one of the 'Police Box' signs at the top, and the gaps around the door caused by my general bad workmanship!

Do these seem suitable for my needs? Is there anything else I should consider?

[symmetal]

I have that model tube heater in my roll-off plastic shed which is a little larger than yours and it keeps everything dry with no condensation at all inside. The only ventilation is the gaps around the doors which seems to work fine. If there is light dew on the telescope after use, I don't bother with a dehumidifier as it will all be dry by the next day even when it's raining outside.

If there is very heavy dewing after use I run a dehumidifier for a couple of hours just to quicken the drying. You really need a dehumidifier that allows an external drain pipe to be attached as the internal tank will be full in a few hours. Mine is a desiccant type as compressor type dehumidifiers don't work at low temperatures. The one you've linked to says it's a peltier type. These have low moisture removal rates (0.5-1.25 pints/day) compared to 15-20 pints for desiccant and up to 50 pints for compressor types of common domestic dehumidifiers. I don't know how well peltier ones perform at low air temperatures for removing moisture.

Even though the inside of the shed is dry, when it's damp outside, the humidity will be still be high compared to inside your home so the  amount of water collected by the dehumidifiers will be significantly larger.

At this time of year the heater is on continuously but the power used is not significant. The desiccant dehumidifier uses about 350 watts on medium setting. 

Alan

[RayD]

+1 with all above.  You'll be emptying it almost hourly if you don't use a type with a permanent drain facility.  Dessicant type is ideal as the are more efficient at lower temperatures.

I don't have a heater at all in my scope room, only the warm room, but then I am fully insulated.

[kirkster501]

Plenty of fresh air flowing through it, open the door whenever you can.  I work from home a lot and have teh door open at least an hour per day.  It soon dries out.

[symmetal]

Thinking further I wouldn't think the peltier ones would work at all if the air temperature was below about +10 degrees or so as the cold side would just ice up.

Alan

[sloz1664]

I have a desiccant type dehumidifier with an external hose. This is connected to a humidstat set at 60%. No dew, damp, rust etc.. Keeps everything just fine.

Steve

[RayD]

39 minutes ago, symmetal said:

Thinking further I wouldn't think the peltier ones would work at all if the air temperature was below about +10 degrees or so as the cold side would just ice up.

Alan

They may have a defrost function like my compressor one in my garage has.  It is automatic but when it is pretty cold it just seems to be in permanent defrost mode.

They do work at low temperatures, but nowhere near as efficiently as the dessicant ones.

[symmetal]

25 minutes ago, RayD said:

They may have a defrost function like my compressor one in my garage has.  It is automatic but when it is pretty cold it just seems to be in permanent defrost mode.

They do work at low temperatures, but nowhere near as efficiently as the dessicant ones.

Possibly Ray.  I've just compared various medium size ones. They all cost about £50, have just an on/off switch, consume about 60W and collect up to 750ml per day. Ideal for wardrobes, closets and small box rooms. They don't mention any defrost feature so implies they only work in heated houses. As you say, desiccant types are only ones that work efficiently at low temperatures. 

Alan

[Penguin]

Cheers, so in summary, that heater is suitable but any dehumidifier would need to be a desiccant type, preferably with a drain hose.

That's really helpful, thanks guys

--- Alistair

[Charic]

For me over the Years,  my outhouses and sheds have just relied on good ventilation, same as my loft, nothing rusts up there, its fully vented and cold in the Winter, but everything is in good order!
 

[iwols]

so can anyone suggest a model of dehumidifier please?

[symmetal]

On 12/22/2017 at 01:49, iwols said:

so can anyone suggest a model of dehumidifier please?

I use this model. It also comes with a drain hose. Running it for a couple of hours after everything is dripping wet with dew is all that's needed to dry it all out. They give off a fair amount of heat along with the dry air which is why they consume more energy than other designs but is why they work in sub zero temperatures. They aren't cheap but are very effective.

Alan

[pmlogg]

I use a Neostar YL-208B which I have powered via a timer, which has an internal battery to retain settings in a power failure. It drains via a pipe ut does have a tank too.

It works pretty well but having read this topic  I am thinking of attaching it to a humidistat so that it can run when needed instead.

 

[nightvision]

I use this one, seems very effective:  Ecoair

 

[RayD]

I use this one, and I think a few others do with good results.  I think where they come in to their own is when your kit is soaked with humidity, and it dries it all out very quickly rather than sitting damp for some time.

For an obsy your size this may be a bit OTT, so any one with desiccant operation and permanent drain should work fine.

[Merlin66]

While in the UK I made use of a heated doggie blanket. Cheap and effective - just thrown over the telescope at the end of the session. It gives enough heat to warm things up and reduce condensation. I've tried both the 12v and 220v types.