Frustration with condensation

[Roysten]

Just had quite a frustrating night trying to image Orion's Nebula. I got my reflector polar aligned and out nice and early to acclimatise. Sadly I didn't get very far, even at high exposure times I got no hints of the nebula.

I brought my scope in and found that all the optics were covered in condensation, which I'm assuming is what's caused the problem. It's a cold, clear night in Hull, I'd say seeing was fairly good, perhaps minimally misty.

I've done a bit of Googling and searching on this forum and found stuff on dew shields and heaters.

I was wondering if people had any comments or advice on how to deal with condensation?

Thanks guys!

[Hicks]

On my SCT the corrector plate will fog up very quickly on most nights without a dew shield and even then that just delays the inevitable. You really can't beat having both a dew shield and dew heater to keep the condensation at bay.

Some people buy little heater guns to unfog their optics but I think avoiding it happening to begin with is the better solution.

Any night where the temperature is close to the dew point you'll likely find optics fogging easily.

BTW I've had a similar experience even with the shield+heater as I try to not run the heater on max to avoid overly warming the scope and causing any haze. Sometimes the weather changes a little quicker than expected and the setting isn't quite high enough and the images start to look like cloud has rolled in

 

[StuartJPP]

As above, you really need a dew shield as a minimum if you are going to be out for any length of time...And a dew heater if you are going to be out for prolonged periods. There's not much you can do about it.

To prevent optics fogging up when bringing indoors I use a lens cap which also has a dessicant inside it. You can leave it in a cooler part of the house to slowly bring it up to temperature.

[cjdawson]

Checking for dew after bringing the scope inside won't work... brining the scope into the warm might have been what caused it to fog up.

 

that said.  A dew heater in combination with a dew shield is the way to solve the problem.  With Newtonian style scopes you need to ensure the the primary mirror, secondary mirror and the eyepiece don't dew up.  As it's effectively an open design (open to the air) all three parts could dew up.

if you get a dew controller with three outputs and get three dew straps you should be golden.   Don't think you'd need to worry about a dew shield for a 150P as iirc it's already got a solid ota which acts as a shield for the primary.

 

if you don't want to spend a fortune of dew heaters check out the diy threads, there are plenty of examples of how to make a dew heater cheaply with parts from eBay, some nichrome wire and an old camping mat.

[Squiddy]

As said, when you brought the scope in, the optics immediatly fogged up.

Anyway, one of best thing I've done is putting all those dew heaters on everywhere. I've had some great sessions this autumn without beeing interrupted by dew. Unfortunatly my camera broke down.

Here is a picture of my new setup: http://astronet.se/phpBB3/download/file.php?id=5326&mode=view
I've just finished setting it up, so the weather will probably be messed up over the west part of sweden for a while...

[Hicks]

Sorry Roysten, I missed the part about bringing it in first. If the issue is condensation after you take it indoors, then a dew heater/shield etc is not the solution to that. They're for stopping it misting up whilst outside (although as others have mentioned, the dew shield likely isn't needed for your scope), but even if you've used those on a scope, once you take it indoors and the cold scope/mirror hits the warmer air, you're going to get wet.

I can't really offer any advice for your scope as I'm not sure what it's like, but for my SCT I cap up the end and then place it into a plastic bag before carrying it inside. I then avoid opening the bag/cap for several hours so that the scope can slowly warm up and reduce the risk of any trapped cool air condensing.

Ideally I'd place the scope in the padded suitcase I have for it, but since it doesn't fit until I've taken the counterweight bars off and they're too fiddly to bother with in the early hours, I make do with the plastic bag and cap.

[MARS1960]

I would imagine that it was dew and not condensation from bringing it in the house though of course it will fog as soon as it hits the warmer air.

Last night i was imaging for just 2.5hrs and my equipment was drenched within 30 mins, all that was clear was ota lens and guide scope lens but i had my dew heaters on those.

look on flo they have a good choice and a controller.

[newbie alert]

Dew sheilds and heaters are a must at the moment...but bringing in from the cold into a warm house will make it condensate..think of it like wearing glasses in the cold and walking into a warm house..it will happen straight away..

[Adam J]

On 28/12/2016 at 14:19, newbie alert said:

Dew sheilds and heaters are a must at the moment...but bringing in from the cold into a warm house will make it condensate..think of it like wearing glasses in the cold and walking into a warm house..it will happen straight away..

yes this.

I use a hair dryer. Periodically during the evening along with a dew shield.

[Astrofriend]

Hi Roysten,

I have refractor and camera lenses, if I don't have a dew heater on them I will normally have dew on them after 30 to 60 minutes, but some nights I don't have that problem. It depents where you are and the weather.

 

Here are my project to fight dew:

http://astrofriend.eu/astronomy/projects/project-heating-band/project-heating-band.html

 

I think you have a Newton telescope. Normally it's the secondary mirror that is the biggest problem. Maybe you could get some idea from my homepage but you have to do it in some different way. I recommend you to buy something readymade from store if you are not used to work with electronics, shortcuts could cause fire!

 

/Lars

[RSM]

Have battled with the same problems from dew. Made shields to go around both ends of my Newtonian reflector which helped from a camping mat. On the primary mirror end it just acts as a bit of insulation. Took the plunge and bought the Astro zap system from FLO. Works a treat for all night sessions. Kept things dew free during the really damp and cold nights recently. Have one on the primary mirror end (8") and one on my guidescope (2"). Bit expensive for what it is,  but would buy again if needed. 

[Roysten]

Thanks for the responses guys! Obviously it's a problem for many at this time of year.

Just to clarify as I don't think I was that clear; I noticed the condensation/dew when I brought the scope in, but I'm pretty sure it was present for the majority of my time with the scope outside as my views were significantly impaired compared to what I normally see.

It seems that a dew shield or dew heater is going to be a must for those types of nights.

Astrofield, your dew project efforts look amazing! Do you find they're effective?

Fortunately I've been able to get out recently and not have the same problem, but I'll give some of these suggestions a try and report back!

[Astrofriend]

Hi Roysten,

Yes my dew projets is a succes for me, even for my portable equipment with 5 volt USB power bank as an energy sourche.

After this I don't had any dew problem, but more equipment to handle in the dark.

 

/Lars

[Ant]

I've owned a couple of Newts, one 150P and another 200P - only once have I ever had one of the mirrors due up on me. That was the secondary mirror while at Kelling Heath one year. It was so wet we may as well been swimming!

I would be extremely surprised if due control for either mirror would be worth the investment. The due that you observed would have formed almost immediately you brought the scope in doors.  If you have a refractor, SCT or Mak then dew prevention is worth every penny. 

What did you get in the images? Can you post one of them so we can have a look?

Ant

[Roysten]

Thanks for the input Ant.

The scope was out for quite a while and there was dew everywhere including my table and metal chairs, everything was icing over, a nice cold night but really too much moisture in the air.

I didn't take any images sadly, but essentially M42 couldn't be seen with my kit when at other times (and since this occurrence) I have been able to see it.

From what you're saying it may not be worthwhile spending a load of money getting equipment, any general advice on keeping the optics clear on such a night, or is it best to just not bother!?

[Knight of Clear Skies]

Clear Outside provides an estimate on the dew point, if accurate this can help with planning when dew is going to be a big problem.

To keep camera lenses from fogging up, I've taken to wrapping the barrel in a sock with a foot warmer inside, secured with an elastic band.

[Roysten]

Cheers for that Knight, I use that site but hadn't seen that part of it, will take a look.

The sock sounds like a good idea, will give it a go!