Dew Control

[Atmos (Colin)]

Hello everyone. Interested in some advice from all you avid astrophotographers that do not have the pleasure of having a permanent observatory, all the thrills and spills that go with it.

Soon going to be purchasing my first proper imaging setup (less than two weeks and counting!) and I am now just starting to wonder about how others control dew on things OTHER than their mirrors/lens', already have my Kendrick Dew Heater for that. What I am thinking about is other equipment like power cables, mount, OTA, camera and computer.

I have only done a little bit of playing around in my backyard so far, never more than a few short hours at a time just becoming familiar with my new (second hand as of a few months ago) mount & camera. So far I've just been putting my laptop on a camping chair, cables on a towel. Thinking ahead to all nighters and the excessive amount of dew that I know will form this time of year, how do ya'll go about keeping everything safe?

At this stage I am just thinking of getting a plastic storage box and throwing all of the power plugs in there and placing the lid on top to keep moisture out. Contemplating a beach towel starting underneath the computer and wrapping it over. Not sure whether I should or need to put anything over the mount, telescope or camera such as a light poncho (the stuff that is near as this as glad wrap).

How do you all go about protecting your precious equipment? Love to hear your thoughts.

[traveller (Bo)]

Hi Colin,
I use the following
Mount with scope (or without), heavy duty tarp. I also have an old sleep bag which I use between the tarp and the scope/mount.
Power I use a plastic box to keep everything inside. Jaycar has a power board heavy duty box (Dribox I think), you can also get similar boxes from 4wd stores.
Laptop I use a styrofoam broccoli box with a face towel "flap". The heat generated from the laptop inside the foam box is sufficient to keep it moisture free.
Hope that helps.
Bo

[bugeater (Marty)]

I shove the laptop under a folded tarp. But it's warm, so it doesn't seem to collect much dew, if any. But anything exposed to the sky and unheated gets damp pretty quickly and has even iced over. But there's not much I'd be too worried about getting a bit damp except the laptop.

[Atmos (Colin)]

Originally Posted by traveller

Mount with scope (or without), heavy duty tarp. I also have an old sleep bag which I use between the tarp and the scope/mount.

I would have imagined that having a tarp and sleeping bag over the top would cause terrible tracking errors with the extra weight?

[traveller (Bo)]

My bad Colin, I thought you are referring to keeping the moisture off the setup when parked and done for the evening
If you want to keep moisture off the scope when running, you can try wrapping a yoga mat around the scope (cut around mouthing rings etc) and secure it with Velcro or rubber bands, same for mount.
Bo

[Atmos (Colin)]

Is it worth while bothering about dew on the telescope and mount while it is imaging over night?

[traveller (Bo)]

I don't stay up very late, but worthwhile wrap a towel around the mount to protect the electronics inside (and around the camera esp dslr).
Bo

[Atmos (Colin)]

Going to be using a CCD but I'll have to do some contemplating on a suitable light plastic, something that doesn't allow water to transfer through.

[DavidTrap (David)]

If the temperature of the object drops below the dew point, wouldn't dew form regardless of plastic being wrapped over the mount? It doesn't "rain" from the sky.

DT

[traveller (Bo)]

If the CCD is a cooled unit, then it will have a extractor fan over the heat sink. By enclosing the unit in a container will increase the inside temperature and reduce condensation, but you still need to cut some vents so some of the warm air can be expelled.

[Atmos (Colin)]

Originally Posted by DavidTrap

If the temperature of the object drops below the dew point, wouldn't dew form regardless of plastic being wrapped over the mount? It doesn't "rain" from the sky.

DT

Giving the system a poncho style thing will create an insulation effect to a degree and although it will eventually cool down the dew should almost entirely collect on the external part of the poncho as opposed to mount and telescope.

I am thinking about leaving the imager exposed because of the fans keeping the airflow going around that area.

[glend (Glen)]

I have heard that a space blanket wrapped around a scope is an effective dew shield. Dew does not fall from the sky but rather moisture condenses on surfaces exposed to the 'cold' of space (the night sky). If you can place something between the scope and the sky then you can stop dew formation mostly. You can also try the quilted windscreen sunshields, I have heard they work. The shroud on my 10" truss newt gets soaked but the mirrors stay dry, and this is the case for most shrouded scopes. Just put a barrier up for the dew to settle on (a sacrifical barrier if you will) and the internals should stay dry.

[AlexN]

It's worth noting, I've had setups absolutely dripping wet during an imaging session and never had a drama. I keep the laptop set up inside one of those 30L storage tubs with a towel that drops over the front to stop light spilling out and keep warm in. That keeps the computer and it's transformer dry. I keep all the power inside a plastic tool box. An extension lead runs from the verandah into the box, contained within the box is a 12v 30A power supply that powers the mount, focuser and dew control. There is also a power board in there that feeds power to the camera and the laptop. Everything else is exposed...I found ccds generally stay dry as the body is usually warm.. I've had moisture running down the length of ota's and dripping onto the ground without problems. So long as you can keep your optics dry you are set.

[gregbradley]

Originally Posted by Atmos

Is it worth while bothering about dew on the telescope and mount while it is imaging over night?

No. I think most scopes are reasonably waterproof.

Dew control is:

1. Fans blowing fresh air over the optics (gets rid of thermal boundaries as well plus equalises the mirror/lens better).

2. Insulating the tube - on the RHA I have thermal blankets which are like wetsuit material that wraps around the tube and has a Velcro fixing. I have used windscreen insulation type material that wraps around a refractor objective area of the tube and that seemed to delay the onset of dew very well.

3. Dew heaters.

4. Dew shield.

A combination of the above works well. I have not seen dew on the RHA since I installed a dew heater. I am not sure if the blankets are needed anymore but I leave them on anyway. Without the dew heater dew seemed to only form right near the end of the night when the scope finally dropped down to ambient. The insulation delays that cooling and so the scope optics are always lagging behind ambient temp drops.

I have found in summer its less of a problem and is more of a winter issue.

The other concern I had about dew was staining of the optics which may be hard to clean.

Greg.

[Atmos (Colin)]

Originally Posted by gregbradley

No. I think most scopes are reasonably waterproof.

Dew control is:

1. Fans blowing fresh air over the optics (gets rid of thermal boundaries as well plus equalises the mirror/lens better).

2. Insulating the tube - on the RHA I have thermal blankets which are like wetsuit material that wraps around the tube and has a Velcro fixing. I have used windscreen insulation type material that wraps around a refractor objective area of the tube and that seemed to delay the onset of dew very well.

3. Dew heaters.

4. Dew shield.

A combination of the above works well. I have not seen dew on the RHA since I installed a dew heater. I am not sure if the blankets are needed anymore but I leave them on anyway. Without the dew heater dew seemed to only form right near the end of the night when the scope finally dropped down to ambient. The insulation delays that cooling and so the scope optics are always lagging behind ambient temp drops.

I have found in summer its less of a problem and is more of a winter issue.

The other concern I had about dew was staining of the optics which may be hard to clean.

Greg.

At this stage all I am most interested is keeping equipment in good condition, not wanting to have any dew issues around electronics (definitely want to cover the EQ6 Pro face plate where all of the connections are. Could simply just use a strip of Gladwrap as a super cheap way of keeping dew off of all those electronics/cables/connectors.

Telescope has a retractable dew shield, buying a dew heater for it next week (should probably get the right size as opposed to a 10" one wrapping around it twice) so I won't have any issues around the lens. Was mostly wanting to keep the rest of the refractor in tiptop condition, unsure whether due could cause any problems there long term. Still likely to be quite some time before I have a more permanent setup going, shed with retractable roof should drop the amount of dew considerably, being semi-enclosed and all. Doing the same thing that you've done with your RHA does sound like a good idea, will have to do some looking into getting materials.

I actually built a small fan unit for my 10" SCT a couple of years ago, slowed it down but it didn't have a dew shield so mother nature still beat my little computer fan. If I do ever have an issue with the 130mm lens I can just attach the fan to the front of the dew shield.

Originally Posted by AlexN

It's worth noting, I've had setups absolutely dripping wet during an imaging session and never had a drama. I keep the laptop set up inside one of those 30L storage tubs with a towel that drops over the front to stop light spilling out and keep warm in. That keeps the computer and it's transformer dry. I keep all the power inside a plastic tool box. An extension lead runs from the verandah into the box, contained within the box is a 12v 30A power supply that powers the mount, focuser and dew control. There is also a power board in there that feeds power to the camera and the laptop. Everything else is exposed...I found ccds generally stay dry as the body is usually warm.. I've had moisture running down the length of ota's and dripping onto the ground without problems. So long as you can keep your optics dry you are set.

That's good to know. This is just me buying my first telescope that I am planning on leaving out all night over and over and over. Little paranoid! Hasn't even arrived yet Picking it up in the next week or two, hoping to have everything setup so I can get straight into it.

Originally Posted by glend

I have heard that a space blanket wrapped around a scope is an effective dew shield. Dew does not fall from the sky but rather moisture condenses on surfaces exposed to the 'cold' of space (the night sky). If you can place something between the scope and the sky then you can stop dew formation mostly. You can also try the quilted windscreen sunshields, I have heard they work. The shroud on my 10" truss newt gets soaked but the mirrors stay dry, and this is the case for most shrouded scopes. Just put a barrier up for the dew to settle on (a sacrifical barrier if you will) and the internals should stay dry.

I actually did something very similar with my 10" SCT. Went down to Riot and bought some heavyish card and taped it around the front of the OTA as a sacrificial dew catcher, worked really well.

[AlexN]

Mine is spending the night outside tonight. It's already pretty damned wet. Optics are clear, I'm going to bed. Will get up again @ 4am to park the scope but everything will stay out there until the morning.

I'm a big fan on the sacrificial card dew shield but if you can find something like 1mm thick plastic sheeting, that's even better. Or the insulating stuff people use for sun protection on their windscreen on their cars. That stuff makes a great long lasting dew shield that also helps catch and eliminate stray light.