How damaging is this stuff?

[Doc]

Following on from Towa wonderful thread about how abrasive this volcanic ash is I was wondering....

What damage would it do to my 16" mirror?

Would it even be worth the risk observing while all this stuff is around.

What do you guys think?

[acey]

I'm not too worried and have been out with the scope a couple of times since the eruption started. A bit of stray grit in a cotton swab will do more damage than a microscopic bit of volcanic glass that can be rinsed off.

The astro author Stephen O'Meara observes on Hawaii and writes in one of his books about how he had to get his TeleVue refractor recoated because of the long-term effects of "vog" (volcanic fog). But for that to happen you need to do several years of observing at high altitude on a volcanic island. O'Meara doesn't seem too fussed about it, and nor do the professional astronomers on Hawaii. People who observe in the Arizona desert or Australian outback must encounter a lot more dust than we'll ever get descending on us from Iceland.

[Towa]

The good thing with a mirror is that you can take it out to wash and rinse.

I would guess that things get a bit more complicated with a lens based optic,

recently Takahashi in America issued guidelines about cleaning the lens on

some of their scopes, as capillary action can draw excess cleaning fluid in between the lens

elements.

I know how some people get about cleaning pollen from their optics, they might

need to go into a darkened room if they get volcanic dust stuck onto the residue from pollen.

Its been interesting listening to the experts on the TV talking about the size of dust.

The bulk of material stuff that fell over the weekend at my location is considerably larger than

the tree pollen that's about. The largest pieces we have collected are 1mm in size.

The picture below is a 0.8mm piece taken from the telescope lens. I'm a bit surprised how far

these larger pieces have been carried.

Nearly all the ash that fell yesterday was the size of tree pollen or smaller.

People will have different risk opinions regarding their equipment, personally I'm keeping my

ED scope inside until the wind changes. The lens is already in need of a good clean and I think

I would be gutted if it ended up with a scratch or mark from a piece dust that stubbornly remained

stuck to the residue already on there. my main concern is that the cleaning fluid, lens residue

and abrasive ash will produce a wet & dry effect on the lens surface, so I'm not taken any chances,

particulary after it marked a binocular objective that I left out in the fall-out and then cleaned.

I already have a 4 inch lens with a mark on the lens after cleaning, while people tell me it won't affect the optical performance,

it's darn annoying to know its there, and I feel that if I sell the scope I would have to do the honest thing and tell a potential buyer about it.

[PeterW]

I'd be more worried about breathing in all those PM10's from the large number of diesels about.

As mentioned just blow any dust off, don't wipe it or it could then scratch. I've been trying to collect some ash, but nothing obvious so far.

PEterW

[Doc]

Thanks for the opinions it's put my mind a little more at ease. Next time I clean I'll blow and rinse before I clean the mirror.