Dew / Condensation

[Leigh81]

Hi all,

I'm sure this has been covered many times before so apologies for this post....

But can some explain the basics surrounding dew / condensation... i.e, when you get, what problems it causes, how to overcome it, how to avoid it...

I have a Skywatcher 150pds

Thanks

Leigh

[Tinker1947]

Fit a Dew Shield, that's a extension to the OTA to delay dew build up on the front lens or secondary mirror, there are dew heaters for all sorts of bit EP's, RDF ect, i use Freezer bags with zips to place over the camera once its set-up, and another with the hand controller and camera controller.

[faulksy]

as said heaters and dew shield is the way to go. also a 12v hair dryer works well

[Merlin66]

Dew forms when the moisture in the air condenses. Any surface below the Dew Point temperature (which varies with the humidity) will attract dew.

The easiest solution for the telescope is to fit a dew shield - this extension "tube" is almost mandatory on SCT and refractors.

Added dew heaters (low wattage heating strips) around the objective lens can help keep the temperature of the lens just above the Dew Point temperature.

HTH

[Leigh81]

I'll probably get dew shields,

How long do I leave them on for outside before taking them off?

[Merlin66]

They would normally stay in place for the whole observing session.

[Leigh81]

oh ok..... confused now...

Ok so whats the best course of action until I can get something

[Merlin66]

Use a piece of foam mat or even some stiff cardboard to make a "temporary" dew shield

[Merlin66]

I see you have a newtonian.....these don't suffer as badly as SCT or refractors.

You may not even have a dew problem.

Have you noticed an really dewing up during observing????

[Leigh81]

I see you have a newtonian.....these don't suffer as badly as SCT or refractors.

You may not even have a dew problem.

Have you noticed an really dewing up during observing????

Thats the thing, I only took delivery last week, had some trouble setting up, but I'm getting there, the weather hasn't been great either so I actually haven't been outside with it yet ... lol

So what I don't want to do, is to go outside set up start observing taking pictures only to find that i got dew

[Merlin66]

IMHO - start with what you have....there may be no problem to solve.

[Leigh81]

Ok thanks -

Cheers for the advice

[themos]

You'll probably not get dew in a reflector at this time. It's worse in the autumn or spring, I find. When it's this cold there's not much moisture left in the air from the daytime.

If the secondary mirror dews up, a quick blast with a hairdryer sorts it out. Some people fit little heaters on their secondaries to stop dew forming in the first place.

[Leigh81]

ok cool, thanks themos

[Kedvenc]

The only dew problems I've had with my newt is on the eye piece. I now keep them capped and in my jacket pocket when not being used; this seems to sort the problem out.