Long-term condensation - how serious?

[lukebl]

Hi,

I know we all have issues on damp nights, with the mirrors and lenses misting up, and there is plenty of advice here on that.

Just wondered what the potential problems of long-term moisture are on our equipment. My telescope is permently mounted on a pier in a timber obsy with pvc roof (see here). With the seemingly endless cloud and damp, I haven't used it much at all. When I checked it this morning, I noticed that the primary mirror is all misted up and the tube is dripping in condensation. I have no idea how long it's been in that state, but it's probably been like that for days and if the weather doesn't clear up it will probably stay that way all winter.

Installing a dehimidifyer isn't really practical in what is effectively a draughty damp shed. Any idea if this will cause long-term damage, and if there are any ways of protecting my kit? How about fixing some silica gel sachets inside the tube? Don't want to resort to bringing the stuff inside, as that would defeat the whole object of having an obsy!

[NGC 1502]

Hi Luke, a clubmate of mine with an 8" SCT in a roll off roof observatory,

uses large bags of silica gel strapped to his scope. He takes the bags indoors

to dry them out.

Your draughty obs would help things to dry out, I think.

HTH, Ed.

[lukebl]

Hi Luke, a clubmate of mine with an 8" SCT in a roll off roof observatory,

uses large bags of silica gel strapped to his scope. He takes the bags indoors

to dry them out...

HTH, Ed.

Sounds worth a try, but where do you get bags of Silica gel from. Seems a shame to buy it, after spending years throwing it away in packaging!

[michael.h.f.wilkinson]

I store my kit i a rather dry garage, but I also chuck in any bag of silica gel I find in any package we get. I once had to get a (tiny spec of) fungus growing on the coatings removed from one of the inner surfaces of a Carl Zeiss S-Planar 4/100mm macro lens. That was costly, and not something I wish to repeat.

[Dave Smith]

Are you sure a de-humidifier will not work? I use this one in my SkyShed POD which has a gap all around the base of the dome and have had no condensation at all this winter and I have it on it's lowest setting.

ELA DD822 Dehumidifier & Laundry Drier | Laundry Driers | Dehumidifiers

I see it was Gear section of S@N magazine this month.

Dave

[lukebl]

Thanks Dave, but way out of my price range right now!

[NGC 1502]

Amazon.co.uk: silica gel packs

Hi Luke, Amazon do silica gel packs, link above. HTH, Ed.

[Psychobilly]

Are you sure a de-humidifier will not work? I use this one in my SkyShed POD which has a gap all around the base of the dome and have had no condensation at all this winter and I have it on it's lowest setting.

ELA DD822 Dehumidifier & Laundry Drier | Laundry Driers | Dehumidifiers

I see it was Gear section of S@N magazine this month.

Dave

Got any idea of the actual runing costs Dave... I need to sort out soemthing better for the obs...

I have got a busy weekend ahead stripping and cleaning the SCT (FCP and Mirrors) and the Frac

Billy...

[Dave Smith]

Got any idea of the actual runing costs Dave... I need to sort out soemthing better for the obs...

Billy...

The website quotes max 620W but that would be in it's laundry drying mode. There is also a medium and low setting and also you can set it to turn off when the humidity is 60%, 50%, 40% and continuous. I have mine set at low and 60% humidity so can only guess at the power. Maybe 150W? I will put a question to the MD who is himself an astronomer.

Dave

[Psychobilly]

Cheers Dave.. the Unibond Humidity stops were working out about £5 a month and coped ok last year but have let me down bigtime this one ho hum

As long as the OG doesn't start filling up the obs with the washing I guess it will be fine .. and I could take out the frost heater I had been using in there as well...

Billy...

[Moonshane]

I got some from Ebay - very reasonably priced too.

[lukebl]

I got some from Ebay - very reasonably priced too.

Some what? Silica gel?

[Moonshane]

oops sorry, yes. Silica Gel In 50g bags from here 7dayshop Silica Gel - 10 Pack (50 Gram Bags) on eBay (end time 11-Feb-11 17:32:49 GMT). seems like the cheaper solution. I would always worry about 'constant' damp in an outbuilding. I wonder if you could also use a battery powered dew strap just to keep the temps up a little on the scope?

[lukebl]

Thanks all. Just ordered some of these.

Does everyone dehumidify their obsys? I hadn't realised that it could be a real problem till today, and haven't seen any threads on this matter before. Many moons ago I visited Patrick Moore's garden observatories, and I don't recall them being very damp-proof, particularly the one which slides apart in the middle!