Condensation problem on lens (and a pic of the moon!)

Kencollins

Hi all,

With the clear sky over the last few nights, and finally sorting out my collimation problem, I have been able to see Venus and Jupiter, and th Orion, Andromeda, and Trianglum Messier objects. It really is amazing what a cheap scope can do when it is calibrated correctly!

At the moment its pretty icy, and frost has formed over the scope. I am cooling the eyepieces in a sheltered area, so they are safe. The big problem im having is that as soon as I put my eye to the eyepiece condensation starts to farm, and is running within 10 seconds. I wipe it with a microfiber cloth, and the same happens again!

I know the scope has to be fully cooled down, but does the same apply to the eyepieces too? Could I leave them inside until I am ready to start viewing?

peterako

I'm not sure if this is the correct way to go but....

I never bother cooling down my eyepieces, just the scope.
I keep the lenses I'm not using in the scope in my utility until I want to use them. And when I sqwitch eyepiece the one that was in teh scope goes back indoors.

When the eyepieces DO get very cold....condensation will form on them.

One simple suggested cure is to blow a warm hairdryer at them for a few seconds.

I usuall just put them in my hand (not holding the glass of course!) for a 20 or so seconds and all's fine again.

Wiping your lenses with any type of cloth is generally not recommended, eyen high quality lens cloths.

Delighted to hear you're enjoying the scope

Peter

Popoutman

I never cool the eyepieces - they don't need to be cold. In some cold places where people observe, heating strips are used on the eyepieces to prevent condensation and icing.

Either keep the eyepieces in an insulated bag (insulated lunch bag or similar is ideal) with a rechargeable handwarmer or two, and you'll be good.

The scopes are left to cool as the "heatwaves" coming from warm optics or warm tubes will distort the incoming wavefront. A warm eyepiece itself will not affect the wavefront, and the benefit of no condensation is more important.

slade_x

Some handy links that can help you

http://www.astro-tom.com/tips_and_advice/dewing.htm
http://en.wikipedia.org/wiki/Dew_point

Popoutman

Note though that condensation can form on objects that have cooled below ambient temperature (due to radiative effects), even when the local ambient temperature is still above the dew point.