Poking around for information on the upcoming eclipse in Europe/Middle East this August I found some really great information at the NASA Eclipse page. In the article for the August eclipse is a page on eye safety which includes a really nifty graphic showing behaviour of some solar filters. It addresses the film negatives issue as well as the cracking filters issue. See below for links.
“Safe” filters (provided you don’t drop them or ‘forget’ to use them) include #14 Welder’s glass, some Compact Discs, SOME film negatives, and aluminized mylar designed for the purpose of filtering sunlight for observation (balloon/space blanket mylar is UNSAFE.)
Read the article for more details, but apparently the major concerns are visible light and near-infrared. The big risk seems to be thermal burns from infrared light, and overstimulation from insufficiently filtered visible light.
It’s true that you could slip and expose your eyeball to the sun for an instant, but I’ve done that before just by looking for a bird or other airborne object and managed to blink or look away before doing permanent damage (yes, I’ve had an eye exam since then, and my vision is great.) I think it is important not to lull yourself into a false sense of security, but at the same time a blanket statement warning off all attempts to use filters is not warranted.
It is true that the safest method is projection, but I could also stab myself while slicing carrots or forget to pull the ripcord when I skydive. If you think you are the type of person who could accidentally remove the filter from your eyes, then don’t look at the sun even with a filter. If you are willing to risk it, just make sure you know what the risk is.
Not that I’m encouraging others to do so, but I watched the last (partial) eclipse through a couple of CDs and I don’t see any worse now than I did before. Once before that I used a couple of sheets of welder’s glass over the lens of a camera, and again no noticeable damage.
Obviously, there IS such a thing as a safe filter… say a 4" slab of lead plate. You won’t be seeing much through that, of course, but there’s got to be something which is both transparent enough to visible light that you can actually see something and opaque enough to visible (and other) light that you won’t damage your eyes.
I think the reason for all the warnings is total eclipses: anything which is opaque enough to be safe probably won’t let you see much at totality, and anything that’ll let you see the corona is probably not safe once totality ends.
I kinda like the NASA’s map of the umbral path through Western Europe. I clearly shows the city of Karl-Marx-Stadt (now called Chemnitz again, but named after Marx in socialist times) as well as the so-called ADIZ (air defense identification zone) right along the inner-German border.
Ever heard of the Reunification? Time to update your maps, guys!
If I can find a cheap fare, I’m thinking of popping over to see the eclipse next week, so I thank all of you for the knowledge I am receiving here. I have two questions:
I already know to go to the path of totality, and air schedules thus limit me to Stuttgart, Munich and Bucharest. Is Bucharest better because it’s closer to the “greatest eclipse” described on the web pages cited above?
Eclipses have been around for a lot longer than cool stuff like welding masks and even pinpoint cameras. Have there been any instances of mass blindness caused by awestruck people staring at an eclipsed sun? Do curious pets and livestock look up and suffer the consequenses?
O.K. that was three questions.
This is not an offer to agree or disagree with opinions, which may be done only by a current prospectus.
You can stare at an eclipse without “going blind” but it will PERMANENTLY damage vision. This was probably less of a problem for illiterate dirt farmers of antiquity.
Im guessing that animals have more sense than to stare at uncomfortably bright objects. But by all means, bring your cat along and check, we’d all like to know for certain.
