Will condensation harm my telescope?

[Skywise]

Sorry - I know I'm asking daft questions, but  . . . . .  I was out in the garden earlier observing the moon for the first time on my first night with my telescope = absolutely spectacular!  Anyway, I left the telescope in the garden to wait for it to get dark so I could use it later this evening, but it started to get very wet with condensation.  Hubby brought it inside because we were a bit concerned that the condensation would harm the telescope (it's a Celestron 114EQ reflector) but now I'm a bit concerned about taking it back out into the cold after being in the warm for a couple of hours.  What should I do?  Keep it indoors and not try using it again tonight, or take it back outside and let it adjust naturally to the night cold before using it?  Thanks for any advice you might have.

[Starlight 1]

Go back out . when done for the night park the tube faceing down with  the cover off for a hour or two inside the house.

Start looking at post on dew heaters your next bit of kit.

[Charic]

Hi there Skywise, welcome to SGL.  when you take a reflector telescope outside, it needs to cool down to the ambient temperature. This will give you better results when observing. When you bring the telescope back inside, it will also appear to have condensate over its surfaces. Just let it evaporate before covering. Telescope will not get harmed. There will be times here in UK when no matter how long the telescope cools, the surfaces may freeze over, time to go back inside?

[RichM63]

Condensation/dewing is a problem that we all experience. As per above, but DO NOT under any circumstances be tempted to wipe the mirrors, this will harm them.

[Skywise]

Thanks for all your help guys - I took the telescope back outside and let it cool back down.  I've been having a very happy time learning how to centre stars in the viewfinder, how to move the telescope around the sky and generally having good fun - Oh, and I saw the Pleiades clearly for the first time - how beautiful are they?  I'm just waiting for Orion to peek up above the roof of the house over the back and for Jupiter to rise!  Very exited and a bit giddy with it all 

[Charic]

Sounds daft but warm air rises from the walls/windows/entrances/exits/roofs, disturbing the air you look through, and although this  may seem excessive precautions to take,  try to avoid looking at something over the roof line? Similar to looking at objects on the horizon,  the  more atmosphere your looking through the worse the effect.

Also you could try cutting some of that camping foam ground sheet ( if you have any - cheap to purchase if you don't have any ) that insulate you from the cold, whilst lying on the ground camping?

Take some and create a tube that slides on to the end of your telescope. This will help prevent some of the dew/condensation from getting near the main mirror, and will also help reduce any stray lights nearby from getting inside the telescope. Also, the darker your space (hiding behind sheds) the better your eyes get accustomed to the dark, this all helps, together with the weather (seeing conditions) to a much better experience during your observations.

[Fish]

When you use your gear outside the cold bits will get wet, and eventually freeze . All the bits that have power as a rule keep warm enough to not get wet. Just keep your scope out as long as you need , until you sort dew heaters use a hair dryer to keep your eyepieces and secondary mirror clear (front lens if refractor) only apply a little heat , just enough to de mist. Keep your hair dryer and extension out of the dew though. When you have finnished for the evening take your scope inside and leave it open and uncovered untill it has dried out.

Glad your having fun :-)

[Stu]

As others have said, don't worry and just enjoy the scope. If the secondary dews up a hairdryer is very handy.

The only things to avoid are putting the scope away before everything has dried off, or wiping the mirror.

Quite often in the winter my scopes end up covered in frost and ice at the end of a session. I sometimes leave them out to dry in the sunshine the following morning if I know it is not going to rain, or bring them indoors to dry.

Sent from my iPhone using Tapatalk

[jefrs]

Ours got well iced up last night (29/30). The mirror stayed clear of condensation but biggest problem was the red-dot finder had to be mopped out with a lens cloth.

The eyepieces I popped into my trouser pocket to keep warm, which worked. Afterwards the contraption was left to air out in the utility room.

I see cute little sachets of desiccant on sale in dummy eyepieces but I've got to laugh. I used the stuff for years and you need kilos of it not a few grams.

I shall probably be looking for heated dew bandages for tube and camera reflex lenses.

[ghostdance]

Interesting -

....I see cute little sachets of desiccant on sale in dummy eyepieces but I've got to laugh. I used the stuff for years and you need kilos of it not a few grams.

Interesting. I keep a small perforated box of desiccant in my eyepiece/finder case and inside my scope carrycase...only a few grammes not k's. Not effective? Should I not bother?

[jefrs]

Interesting -

Interesting. I keep a small perforated box of desiccant in my eyepiece/finder case and inside my scope carrycase...only a few grammes not k's. Not effective? Should I not bother?

I'm a retired physicist-engineer, I've used desiccant for years to keep delicate instruments dry. In a sealed system maybe 50g will do to preseve small parts but a telescope tube is not sealed. For bigger stuff we used buckets of the stuff, like half a dozen 500g bags and then tried to seal it all up: losing battle.

I'd just bring the kit indors where it's warm and dry. Don't pack it away in its case until it has aired out nice and dry. If you must buy desiccant then scout around your neareast industrial trading estate for a supplier of sensible size bags, it's as cheap as chips.

My trouser pocket worked: no mist on the lens at all. Only hair dryer wife will let me use is the B&D paint stripper and that's so not going to happen.

I had a cunning plan and used Autoglym High Definition Wax on the tube and plastics (not the glassware!). It's expensive but I do the cars with it every four months or so. Carnauba wax can set as hard as concrete but it repels moisture by stopping dew from forming beads which turned into slabs of ice on me. That seems to work too but I shall still seek anti-dew heater collars. Other old pro-hat was working as a polymer chemist for a few years.

Hang on, I've got several large rechargeable batteries for garden tools and bicycle lamps, and I've wound furnace heaters before now, All we need now is a rheostat or controller unit. (it's usually cheaper to buy ready made stuff).

[ghostdance]

Like the idea of the Autoglym!

I have brought my scope and eyepieces indoors over winter - seemed my garden shed could get damper than I thought.

Hmm....rechargeable bike batteries - they could work to power a dew strip/ribbon (is that what they're called?). Wonder where my old off-road lights are?

[StarcrazyGeoff]

I don't think the garden shed is a suitable place to store you scope.  My shed at the bottom of the garden can be like a fridge in the winter and as hotter than a greenhouse in the summer. Besides it gets full of spiders and other creepy crawly's, that get in there to hibernate. Best kept indoors, when not in use. 

[Jannis]

My scope have been standing outdoors for 2 years constant now. The scope and mount is working fine still, but some nuts and screws are rusty. Electronics seems fine, but i've had to replace a coupple of cable due to corrosion on teh connector pins. I always park my scope in a flat angle, but after i cover the rear end of my OTA with aluminum foil and had my dew heater in the front i've never had issues with water or dev on any of the mirrors.

[greglloyd]

Ours got well iced up last night (29/30). The mirror stayed clear of condensation but biggest problem was the red-dot finder had to be mopped out with a lens cloth.

The eyepieces I popped into my trouser pocket to keep warm, which worked. Afterwards the contraption was left to air out in the utility room.

I see cute little sachets of desiccant on sale in dummy eyepieces but I've got to laugh. I used the stuff for years and you need kilos of it not a few grams.

I shall probably be looking for heated dew bandages for tube and camera reflex lenses.

I had a serious condensation problem with my 12" dob in the shed. The mirror was soaking most days. I'm now using 150g Silica Gel (6 x 25g sachets) attached to the inside of the front dust cover on the scope and they sort the problem right out! I have a cover on the rear of the scope also so that the silica can be more effective (i.e. it dries out the trapped air in the scope).

[baggywrinkle]

If you have the type of silica that changes colour it can be baked in an oven at 150C for an hour or so to regenerate it.

I use this type in a piece of Rh calibration equipment and it works quite well.

Metal tubes (OTA's) mirrors and lenses do not cool down just to ambient, if they did it would not be a problem. They cool by radiaiting heat off and this cools them to below ambient which depending on the conditions will hit the dew point and then of course water condenses out as you change from gaseous water vapour phase to liquid phase behaviour.

The difference between ambient T and dew point T does not have to be large, in fact as little as a single degree can be enough.

[chris_suffolk]

Visited another member off here yesterday, he runs an electric blanket on low and a dehumidifier in his Obsy to keep condensation at bay. Keeping scope outside otherwise must have an effect

[jefrs]

If you have the type of silica that changes colour it can be baked in an oven at 150C for an hour or so to regenerate it.

I use this type in a piece of Rh calibration equipment and it works quite well.

Metal tubes (OTA's) mirrors and lenses do not cool down just to ambient, if they did it would not be a problem. They cool by radiaiting heat off and this cools them to below ambient which depending on the conditions will hit the dew point and then of course water condenses out as you change from gaseous water vapour phase to liquid phase behaviour.

The difference between ambient T and dew point T does not have to be large, in fact as little as a single degree can be enough.

It does not have to change colour, you can weigh it. I keep a coulple of 1kg bags in the car, when they get to 1500g they need regenerating on a radiator.

Heat and tremperature are misunderstood subjects. You need to consider thermal conductivity: metals readily conduct heat which makes them feel cool when at ambient. Ye cannae break the laws of thermodynamics ;-)

[jefrs]

Visited another member off here yesterday, he runs an electric blanket on low and a dehumidifier in his Obsy to keep condensation at bay. Keeping scope outside otherwise must have an effect

I have an electric oil-rilled radfiator in the workshop, it keeps dampness off my tools, I know first-hand that these work in a shed

Set at zero it will maintain a room frost-free but that is too cold for me.

[baggywrinkle]

It does not have to change colour, you can weigh it. I keep a coulple of 1kg bags in the car, when they get to 1500g they need regenerating on a radiator.

Heat and tremperature are misunderstood subjects. You need to consider thermal conductivity: metals readily conduct heat which makes them feel cool when at ambient. Ye cannae break the laws of thermodynamics ;-)

We use the colour change type as it tells the user that they need to regenerate.

We have a free Rh & Dew Point calculator on our website http://michell.com/uk/support/sware-downloads.htm quite useful to work out the dew point of the day/night. Use the Relative Humidity button.

[graemlourens]

There is another post too about how to handle the scope.

http://stargazerslounge.com/topic/233707-looking-after-the-scope/

Check my answer (nr 4).

Regards, Graem

[cotterless45]

I keep all my gear in a garden shed. However the Newt have reptile heating pads on the back of the mirrors.

These provide a gentle heat at 6W. I also try and open up the shed to circulate air and keep the temperature down when it heats up. You can get them quite cheaply on ebay from China, about a third of the price of pet shop ones.

Initially without the pads I found insidious dew/ humidity on the mirrors when temperatures changed. If I'm sure of observing that evening, I remove the pad and open a door up,

Nick.

[jefrs]

We use the colour change type as it tells the user that they need to regenerate.

We have a free Rh & Dew Point calculator on our website http://michell.com/uk/support/sware-downloads.htm quite useful to work out the dew point of the day/night. Use the Relative Humidity button.

We used the colour indicator desiccant in many of the instruments the department calibrated, useful but it's not the only method. You can buy bagged or loose silica gel right cheaply from industrial suppliers. Big bags, bigger is better, too big is just right. When I retired I was running an international primary calibration standard. Our reference Rh, T&P meters were calibrated by primary lab. I intend to get several half-kilo bags for the scope and camera aluminium storage cases (not the carry bags) and rotate them in and out; about the size of a bag of sugar. A cloth (lens) bag full of dry rice will also work but not nearly as efficient, so will common salt but you can get corrosion everywhere.

I put two 1 kilo bags intended for a car in the car. The maker reckoned one bag was enough, two is not enough, I estimate at least six are needed in wet weather. These are regenerated on their weight; when they go over 1500g put on radiator. It is heat input that regenerates them not temperature (chemistry): you can use a low-low (plate warming) fan oven; we used lab convector ovens at work.

[jefrs]

I keep all my gear in a garden shed. However the Newt have reptile heating pads on the back of the mirrors.

These provide a gentle heat at 6W. I also try and open up the shed to circulate air and keep the temperature down when it heats up. You can get them quite cheaply on ebay from China, about a third of the price of pet shop ones.

Initially without the pads I found insidious dew/ humidity on the mirrors when temperatures changed. If I'm sure of observing that evening, I remove the pad and open a door up,

Nick.

Interesting (!)

Of course the other big shed problem is mould, we can get mould on lenses as well as my leather bike saddles, and a new big shed (with mains power) in the spring is planned for me (I'll have to clear extra ground and shift a pair of 1 tonne compost bins, I've already booked a mate to help). My old shed has disintegrated.

[nicks90]

my 12" dob lives in my very drafty / slightly damp concrete slab garage.

its fine.

it gets dragged out and its already at ambient temp, it gets soaking with dew whilst observing and then gets dragged back in the garage once i;m done.

Next day it always seems to be dry (ish) and ready for action again.

Some of the exposed allen screw heads on the dob base have a spot of rust on them, but other than that it seems completely unharmed by living in there.