temperature and humidity control for remote observatory

[Somnium]

I just wanted to get the thoughts from those who have observatories, do you manage the temperature and humidity during non observing times. i would imagine that a few 40 degree aussie days would not be fantastic for sensitive equipment. if so, what solutions do you have?

Thanks

[E_ri_k]

Hey Aidan, this has also been a concern of mine, although my OBS is not remote, so when it gets really hot I just open the door and get a draft going. My shed is dark blue, so it gets really hot during summer, to the point where my mount would get very hot to touch. I never had any problems with equipment failing due to it though. Overnight condensation was also a problem.

I installed an extraction fan and venting close to the cieling, which didn't really make a difference!

I'm considering something like this:
http://www.ebay.com.au/itm/Roof-Vent-Fan-3000-25W-PV-Heat-Extraction-ROOF-MOUNTED-3000-m3-h-cap-/301014803886?hash=item4615e165ae

It's a bit pricey, I recall seeing one for around $400, but can't find it?
I'm also interested in others input.
Erik

[Shiraz]

Big issue. Used reflective foil insulation in the walls and ceiling of my ROR to keep out radiant heat in summer - works well enough to protect equipment even on fierce days. I have a small aircon that I run for a few hours before dusk on very hot days to get the interior of the obs down to night temps - can get better seeing if the floor and mount are not hot while trying to image.

Have an issue with humidity - the interior of the obs gets dripping wet with dew some nights and when the lid is closed and the sun comes up, all that water evaporates and then condenses on the mount and mirror (which remain at night temps). Still working on that one - a vent did not help much and next trick will be to run the aircon again in the mornings to dehumidify the air as the sun comes up.

Long term, the disposable chloride laundry dehumidifiers seem to work OK when the lid is closed, provided there is not too much outside air making its way in.

[Somnium]

Thanks for that Ray, i am thinking i will have to run a dehumidifier and maybe an aircon. i do have silver insulated wrapping on the ob walls and roof so i might just need ventilation for to maintain a decent temperature, but the dew has been bad recently. test and learn i guess

[Paul Haese]

I only have sisalation under the roof sheets in the roll off roof and nothing in the dome. The dome is two pack painted white and helps to keep the heat at bay. It does get very hot in both observatories on really hot days in summer. Above 45 degrees often. I usually leave everything in place and just wait until dark to open the roof to dissipate the heat. If I am imaging I open the shutters about an hour early than I would in winter. Never had an issue yet.

I get rivers of dew at my site too. Every night it is clear there is lots of dew. It is rare that there is not dew. Most nights there is dew dripping off the eave sheets around the house, that would indicate how much dew is about. Trying to alleviate the condensation in the observatories would be a futile task, I have never seen another site with more dew than what I get. I suppose that is what I get with water all the way around me on a flat plain. I run my dew heaters on maximum power in each observatory during imaging seasons and have the dew heater on for over 2 hours prior to opening the shutters. If I don't run the heaters of full power I get dewing on the optical surfaces. To that end I have not seen any really adverse effects so far in last few years with these new scopes. Over the time since 2008 I have not seen any issues with all the equipment that has been on site with regard to dew levels.

Personally, I don't think it is either issues are a problem, but if you want to do something about these two factors then you could put a whirly bird on the roof to keep the heat down and it would also create enough circulation to remove dew and condensation in your observatory. Using something that chews power is probably not very economical, but a solar powered system would pay for itself in no time. With lots of dew be careful about screws and bolts that are not stainless or aluminium. Rust will creep in.

Hope that helps.

[pmrid]

Aiden, I have a fairly large (in floor area anyway) obs - 5x4 metres with a hip roof. And I'm in the bush. To deal with the heat, I fitted a second roof on top of the original - separating the two with heaps of insulation. It dropped ambient inside the obs down by a considerable margin. Neever actually measured it but it was enough to justify the effort and expense.

As for condensation, there's not a lot you can do when the roof is open except for dew bands on the scopes etc. When the roof closes, and the equipment is wet from a night in the open, I make sure to put enough covers over the gear to keep dust off the optics but I don't put lenscaps etc back on so what dew there is can evaporate away and that's as much as I can do with major interventions such as dehumidifiers. I figured those are only going to be effective if your obs is well sealed. Mine isn't. I prefer to encourage airflow.

Peter

[ZeroID]

I know conditions over here in NZ aren't quite the same re heat and dew but can I ask if any of you have a floating floor ? ie a floor raised above the subbase concrete, pavers, ground etc.
Dew can be an issue over here at shutdown but very rare at opening up.
My floor is about 250mm above the large concrete slab that forms the base for the pier and I have to say that the cooler air that flows beneath seems to help both dew and temperature.
I contemplated the double skin roof idea but seems unecessary over here but light coloured exterior walls and roof ceratinly helps and I've seen the idea of planting low hedge like vegetation close to at least North facing walls to lower exposure.

[Somnium]

My observatory does not have a floating floor, i have a huge concrete slab on which i built. also, i am not concerned about humidity during an observing session, i will use my dew control system for that, it is more about protecting the equipment during the day. i am thinking about having a dehumidifier kick in when the roof is closed and the humidity is above 50 -55%

[pmrid]

Yep. My floor is 300 or so avove the earth and gets a good air flow. The rabbits love it. A colony seems to bevsetting up housebthere.
Peter

[glend]

I have a solar powered exhaust fan mounted up near the peak of the skillion roof and it helps with both temperature and humidity. My floor is raised off the ground on posts with the pier extending up through a hole. I only seem to get condensation on the concrete pier but the dehumidifier takes care of that each morning.