Rain on optics?

[Ziggy]

Hi Guys,

Has anyone been caught in the rain before, and had it fall on their scope? If so, is it a drama? Bit late for me to ask this now, but last night, I was taking a look at Orion, when I decided to change eyepieces, so over to the case I went. As I was about to get the next piece out, I felt a drop on my head....from nowhere a cloud had come across with just enough rain to be a nuisance.

Now, hindsight is a great thing, but my first reaction was to seal the eyepiece case, then I realised I needed the cover for the diagonal, as it was uncovered with nothing in it, so attached that. By the time I got the cover on the front of the scope, (SCT), some rain had gotten onto it.

It was just droplets, not enough to run or anything. Anyway, I left the cover off over night under a ceiling fan to let it dry. It seems ok, just helped to emphasise how much dust is on it, though a couple of spots look like they're wet, though I'm pretty sure they're not...if you know what I mean.

As I said, everything looks ok, so I doubt it's done any damage, and I know you have to wet it to clean it anyway, just not sure if I should have dried it at the time, or if letting it dry naturally was the right thing to do? I'm pretty sure I would have scratched everything if I'd tried to dry it. I'm presuming it's a bit like getting dew on it?

And the rain has set in today, so might be a while before I can test it again. It's one of those things where you know it's ok....but you need some positive reinforcement ;)

Any suggestions or thoughts appreciated.

Thanks,

Glen

ps: Hope this is the right forum for this topic!

[Merlin66]

Sounds like you did the best thing! Slight marks/ dust are better than scratched optics every time. Such are the trials and tribulations of being an astronomer!!

[voyager2]

rain water on your corrector is no problem at all, rain water is pretty pure too so it shouldnt leave to much residue either, just leave it till the corrector needs cleaning, its really no worse than dew.

[h0ughy]

not true, if you live in a built up town or city area or on the coast with salt spray as well, or an industrial area is nearby, the water will be slightly acidic, and also picks up dust and other contaminants in the atmosphere on the way down if it is at the beginning of rainfall after a dry spell. The acid will slightly etch the corrector coatings. Drying immediately with a hair dryer will help negate the piting problem. Lets just say experience and a bit of digging on the net in this area when it happened to me.;)

Dew forms close to the ground and hasn't had time to pick up the dust and other impurities, unless your in a really bad coastal or industrial area, or its carried by fog from said areas.

[Roger Davis]

In Cairns I don't think it would be so bad. Only a couple of drops wouldn't matter so much. If you are really paranoid, take out the mirrors and rinse then with distilled water and allow to dry. Then reinstall, recollimate and continue on. I reckon we had mud on the 27" a couple of times and a simple wash firstly with tap water and then distilled did a wonderful job.

[h0ughy]

I should have looked where he was from, but still cars are a contributor to acid rain. But the salt air would be a concern if right on the coast, I know seaspray can be outright nasty sometimes.:)

[Ziggy]

Hi Guys,

Thanks for the replies. Thought I was going to have the chance to test it again tonight....but the weather intervened again. Anyway, I think I'll just leave it as it is for now, and see how things look when I next get to use it. As I said, it was only a minimal amount that fell on the corrector plate, and it looks ok as far as I can tell, so I'll just leave it for now.

Oh, I don't think we have to worry to much about acid rain or pollutants up here, though the salty sea air is a concern. I'm about 2kms inland.

Anyway, I guess I was a bit more concerned last night, as it wasn't something I was expecting, but I think it'll be ok. From what I've read, the coatings and things seem a bit more resiliant than you'd expect, so if they can survive mud, a bit of rain shouldn't hurt :)

And as anyone with an SCT would know, if you look at the front in the dark, it looks absolutely flawless. The mistake is looking at it with a light shining on it ;)

Thanks again for the responses guys!

[EzyStyles]

talking about rain on optics, what if rain on motorised mount? will this be an issue?