Telescope maintenance

[Garry Murphy]

I was told that it was advisable to place your telescope outside , for it to climatise itself to the temperature and humidity outside , for about 1 hour . I did this but I could not really see that well as there was a lot of condensation on the lenses . The metal outside of the telescope , a 4.5 " Celestron , was exteremely wet , and when I wiped its outside , the cloth was actually wet! Any suggestions .By the way the external temperature was about 1Degree Celcius.

[Tinaa]

I moved your question. I think it'll get more responses here.

[TheAstronomer]

Awww, man... What can I say besides "been there and done that"? It's part of a learning process, so don't worry!

You didn't specify whether we are talking, reflector, refractor, or mak/cas... So I'm just gonna' give you a brief go at any or all of them, ok? Once it's dewed, you can't do anything about it except correct it in the way that is least damaging to the optics. If it's a mak/cas? Use a hairdryer to gently blow away the moisture from the optics. If it's a refractor? The hairdryer will also work, but it's best just to put it in a well-ventilated area and let it dry naturally. If it's a reflector? Make sure to leave all the caps off and leave somewhere there is an air current.

I think one of our first responses is to take the daggone thing right back inside and that can sometimes make it worse. A reflex is to wipe things off, and that is worse yet. Both corrector plates and lenses are coated, so it's just best to let air do the work and the clean them if necessary when everything is dry. For a reflector? Condensation marks are just a battle scar and can be cleaned periodically. Rule of thumb for any scope... Don't worry about cleaning the optics until at least 10% of the surface is obscured. Even the most careful of cleanings is taking a risk.

Solution to keep this from happening again? Steady cool down... Change the scopes environment in storage. For example, if the indoors is humid and the outdoors is cold? Try storing the scope someplace much cooler... Like an unheated garage or a vehicle. You'd be surprised at how much differently your scope will act if you take it out a few hours before you want to observe and just place it in your car before you're ready to set it up for final cool down. The same will work in reverse, for this is another common problem. For scopes kept in an airconditioned home, you go out on a summer night and the thing sweats worse than an iced-tea glass! Try taking it our during the day and placing it in a shady garage, or storage shed. (hey, i'd say the car, but you'd better be using the trunk and not the back window!) Just the subtle changes in environment over a long period will really help.

The same holds true of your optics, mon ami. Keep your eyepieces cooling or warming up gradually. Keep a few silicon packets in your eyepiece case to help keep out extra moisture.

Until then? I'd rather shake the hand of the man who took the scope out than left it in!!!

At your service,

~T