Condensation on the scope

[Pete58]

I put my new 200p Newtonian with EQ5 mount out early to cool down, but must have done something wrong. when i cvame to use it all the eyepieces and the finder scope had condensation on them and i could not see anything. What have i done wrong please.

Thank You

Pete

[Dave In Vermont]

I'd suggest keeping the caps on your eyepieces until you actually are about to use them. Same for the finder. You've done nothing wrong - you live in a place where dewing is a common bane to all astronomers.

Wiping the eyepieces off won't help - just bring them inside and let them dry naturally. Same for the finder. If the mirrors in your 200p dew-up as well, look into a dew-cap extension for the OTA, and possibly a heater for it.

All things must pass,

Dave

[Physopto]

As Dave has said nothing wrong. You really need a couple of dew heaters for the scope and eyepiece. Welcome to the world of astronomy. We all get this problem at times. More so than not. Have a read through the forum about dew heaters and dewing up. You will soon get the picture. 

Derek

[laudropb]

This perfectly normal in our part of the world. Always cap your eps when not in use and the same with your finder. If the finder proves to dew  lot during a session then you can clear it by using a travel hair drier to gently blow away the dew, but always use it at its lowest setting. Eye pieces can be kept capped in a pocket where body heat will help keep them clear, but I use a hand warmer pack in my ep box. After a session let every thing dry off naturally indoors. Your scope should be left uncovered  pointing towards the ground so that any condensation will not run onto the mirror.

[Bruce Leeroy]

I never seem to suffer from condensation on the mirrors or eyepieces, I store my scope on a cold tiled floor (inside) I also keep my eyepiece case closed and flat to the cold tiles. I will get condensation/frost to the outside of the tube but the mirrors stay perfect, 3 degrees here last night and no problems and -1 to -3 degrees a couple of weeks ago with the outside of the tube coated in a lovely fern like frost(3 hour session). I find condensation only a problem if I take an eyepiece into the house/warm area without the covers on or if i breathe over them when I'm observing. My advice is to keep the scope/eyepieces cool and out of sunlight during the day and be careful that when your observing you don't breathe heavily over the eyepiece. Cap your eyepieces outside (unless there covered in condensation) pack them in your case and close the case before coming into any warm area.

I don't use any dew heaters or shield but you may benefit from them!!

 

[pipnina]

I don't recall having problems with dew when observing... But when I bring my scope back indoors the metal tube gets quite damp.

What conditions cause dew? Does it just need to be colder than it's ever been where & when I observe? (Don't think I've been out in negative temps, about 1-2c is about the coldest) does it need to be humid as well? I don't go out on humid nights (usually coincides with poor transparency)

[Bruce Leeroy]

6 minutes ago, pipnina said:

I don't recall having problems with dew when observing... But when I bring my scope back indoors the metal tube gets quite damp.

What conditions cause dew? Does it just need to be colder than it's ever been where & when I observe? (Don't think I've been out in negative temps, about 1-2c is about the coldest) does it need to be humid as well? I don't go out on humid nights (usually coincides with poor transparency)

Cold surface meets warm surface = condensation. The bigger the temperature difference the more condensation forms.

I think the key is extreme temperature differences if you can keep your scope cool through the day your good to go but if you can't then you probably need heaters to ward off the cold air.

 

p.s I'm no seasoned observer like the posters above me !!!

[Pete58]

The odd thing is that i did have the caps on everything and the eyepieces indoors, i took them out and took the caps off and everything just seemed to dew up, b ut i will look into getting a dew heater.

Thank You

Pete

[brantuk]

I keep my eyepieces outside with the scope but under cover of a flight case, then pop one in my pocket for five mins before use. I've never had a primary dew up but I do have a secondary heater and dew shield at the other end. You do have to judge how much moisture is in the air on the day. This is why I keep away from water (lakes, rivers etc) when observing. Of course you can go mad and put heaters on everything ep's, finders, and secondary etc. But a bit of experience and judgement of conditions is mostly cheaper - sounds like you weren't outside very long - give it a bit longer (30mins) to cool down next time.