eclipses and blindness

Is it more dangerous to look at the sun being eclipsed than to look at the sun for the same length of time under normal circumstances?

No, of course not. If you could manage to keep your eyes wide open and stare at the uneclipsed sun, you would certainly fry your retinas. What makes eclipses dangerous is that they are less bright, allowing you to stare, and interesting, making you want to. You will fry your retinas more slowly, but you will still fry them.

On the same line, looking at the sun in a mirror is obviously stupid; just how much sunlight is reflected into my eyes by cars on a sunny day? Not only the damn chrome, but the windows seem to be at just the right angle to reflect the sun into my face. You can't face certain directions in the city some days without keeping your eyes thoroughly averted to the ground, lest you end up squinting and tearing. How much does my risk of cataracts increase because of this idiotic source of UV?

Umm, I use sunglasses.



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My last post was a comment on APB's post. I don't use sunglasses to stare at eclipses, or the sun itself.



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Lazy:
It's definately dangerous. My dad has a hole burned in his retina from looking at a solar eclipse when he was young.

But to your question, the answer seems to be No: Given that you could only look at the full sun for a fraction of a second, looking at an eclipse for that same fraction is less dangerous. But the real answer is Yes. If you're fortunate enough to be in the shadow, your pupils will be wide open due to the mostly dark conditions. Then, any direct sunlight that peeks around the moon (through valleys or as the eclipse is ending) is gonna hit your retinas at full intensity. So if anything, it's more dangerous to look at eclipses, because you're led into a false sense of security.

A similar effect is seen with rear-view mirrors. In broad daylight, a driver's headlights behind you will be noticable but not irritating because your pupils are very small. But at night, the same headlights will bother you because your pupils are wide open for the general darkness.

AWB:In broad daylight, a driver's headlights behind you will be noticable but not irritating because your pupils are very small. But at night, the same headlights will bother you because your pupils are wide open for the general darkness.
Umm, I think this has more to do with the fact that the driver behind you will most likely have his headlights off during the daytime and on at night.

Looking at the sun while it's high in the sky will fry your eyeballs, eclipsed or not. It's only a matter of time. Who among us has not cast a furtive glance heavenward and been rewarded with an apparently indelible afterimage? It's scary how quickly that "idiotic source of UV" will make you pray fervently for a retroactive screen-saver.

What never fails to amaze me are the people (not you, Beer) who think (invariably learned from a FOAF) it's ok to look at an eclipse through sunglasses or photographic negatives - these devices only buy you a few split seconds before your retinas are burned beyond repair. The only really safe way to look at an eclipse is to use a telescope or binoculars to focus a reflected image of the event on a sheet of plain white paper. (Works for full sun, too - good way to see sunspots, even a five and dime 'scope will do).

Reminds me of a sign supposedly spotted in a college lab:

"Do not look directly into laser with remaining good eye."

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The overwhelming majority of people have more than the average (mean) number of legs. -- E. Grebenik

Just wanted to mention that there will be a partial eclipse in the UK on 11 August (total eclipse for the lucky folks in Cornwall and south Devon) if anyone would like to experience first-hand burning their retinas by watching the eclipse through sunglasses, smoked glass, photographic film, or binoculars (none of which will protect you).

Strainger replied to my quote:
AWB: In broad daylight, a driver's headlights behind you will be noticable but not irritating because your pupils are very small. But at night, the same headlights will bother you because your pupils are wide open for the general darkness.

Strainger: Umm, I think this has more to do with the fact that the driver behind you will most likely have his headlights off during the daytime and on at night.

Um, right. What I meant to say was that headlights turned on in the daylight aren't as irritating as at night.

Strainger 'Umm, I think this has more to do with the fact that the driver behind you will most likely have his headlights off during the daytime and on at night.'

That depends on where you are. In Sweden it is illegal to drive with your headlights off at any time. So everyone drives around with low beam on during the day. Not that they enforce the rule vigourously but all cars sold in Sweden have no way to turn the lights off. It also means that one can't leave the car lights on and drain the battery without having the engine on. It is also why most volvos (at least in Australia) have lights on all the time.

Using the numbers from OSHA non-ionizing radiation MPE the maximum power
density safe for a .25secnd viewing is 25W/m2. The sun at miday has a
power density of 1400W/m2.
Checking Oakleys site, their $140 black iridium sunglasses allow 8% transmision which brings
the sun down to 112W/m. So the sun would need to be about 80% obscured for you to safely view it
for a quarter second. Note that these are the darkest lenses the sell, and others range from 25% - 60%
transmission, so using sunglasses to stare at the sun is not recommended

An NDF2 that should bring the power down to 14W/m2 which should ve safe for extended viewing,
As I remember, these can get a bit spendy though.

And of couse they say "dont stare at the sun during an eclipes" because people usually know enough not to stare at the sun at all because it so figgin bright, but an eclipese might tempt them to be stupidly force themselves.

There are solar filters for telescopes that will allow you to safely look directly at the Sun I'll say it again - the "only really safe" way to look at an eclipse or the sun in general is by reflected image.

Solar filters and other optical means of obscuring the greater part of the visible solar radiation have been known to fail (crack, shatter, whatever) during observation, and god help the poor doofus who has his eyeball aligned with that refracted or reflected magnified solar disc.

Same with welder's lenses or other devices. Why take the risk of having your eyeball(s)
at F 1.4 for 1/60th of a second when you slip and remove the lens from the light path or the cheap-shit googles you bought from The Acme Co. drops a lens in your iced tea?

Never look directly at the sun under any conditions. It's just not worth the risk, period.

Uh.. that's goggles.

I will partially disagree with Nick, only because I find him brilliant, yet open to suggestions. ( How's THAT for sucking up, huh?). There is another safe way. I have used it my whole life, aside from one atrocious accident, but I digress.This came from Daddy. Daddy was the Science Editor of the Evening and Sunday Bulletin in Philly, a fine paper, before its demise.
Take a shoebox. Punch, or cut a small hole in one end. Take a small sheet of aluminum foil, and tape it over the hole you made. Take a pin, and make a PIN-HOLE ( get it? ) in the foil. Look at the inside of the shoebox, at the far end from where you made the pinhole. Voila- you can see the tiny circle of the sun,,,and as it goes to full Corona, you can see the sun disappear. Totally safe, your head is tilted DOWNWARDS, away from the sun, looking at the small image of the dot of the sun, that is passing through the hole in the foil.
Now, on to real stupid type folly. I was shooting a job outside of Grand Central Terminal when the last Total Eclipse happened. I was excited, to be sure. We took a lunch break, film crews being what they are ( we march on our tummies ). I walked inside GCT, and was greeted by an amazing sight. There are hundreds of TINY windows along the top of the walls, where they meet the curved ceiling. EACH window acted as a pinhole viewer, as I have described. There was this lovely and surreal path of crescents....in a line, on the floor. People stood, looking down, silently. Quite the thing.
Then, I walked back out, and had the bright idea to shoot footage of the eclipse. DUH, the gaffer holding a Neutral Density gel moved it away too fast, flashing my right eye....and making me quite nauseaous. The afterimage lasted over two days, and the headache and nausea a day.
Use a pinhole, or look at CNN !!! OR- go to Grand Central, in the main room..and feast your eyes. :)
Typer

I'm reminded of the Peanuts storyline wherein Linus, in preparation for an eclipse, warns everyone of the dangers of looking at it through any kind of filter. He rigs up a pinhole gizmo like the one described above (Lucy to Schroeder: "I'll bet Beethoven never would have thought of anything like that!"). In the last strip, Linus is standing outside in the pouring rain. Lucy walks up and says, "So how's the eclipse?"

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---Red Green

The only really safe way to look at an eclipse is to use a telescope or binoculars to focus a reflected image of the event on a sheet of plain white paper. -- Nickrz
There are solar filters for telescopes that will allow you to safely look directly at the Sun. We watched the eclipse of July '91 with such a filter. It wasn't total where we were (Tucson, AZ), but it was pretty close. The filter probably would have made a total eclipse too dark to see. In high school, I briefly looked at a partial eclipse directly thru a welding mask.

I'll say it again - the "only really safe" way to look at an eclipse or the sun in general is by reflected image.

Im sure you meant diffuse reflection. Smooth surfaces can approch 100% reflected power depending on the viewing angle.

i.e. Make sure the reflecting object isn't too shiny.

Rilchiam, which is one reason I think that in later years, Lucy will be known as #31899412, or find out personally where Mr. Hoffa is.

Personally, I say, point a camera up in the right direction with a filter, and take pictures....they last longer. :)

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>>Being Chaotic Evil means never having to say your sorry....unless the other guy is bigger than you.<<

---The dragon observes

Nickrz writes:
What never fails to amaze me are the people (not you, Beer) who think (invariably learned from a FOAF) it's ok to look at an eclipse through sunglasses or photographic negatives - these devices only buy you a few split seconds before your retinas are burned beyond repair. The only really safe way to look at an eclipse is to use a telescope or binoculars to focus a reflected image of the event on a sheet of plain white paper. (Works for full sun, too - good way to see sunspots, even a five and dime 'scope will do).

[later post:]Solar filters and other optical means of obscuring the greater part of the visible solar radiation have been known to fail (crack, shatter, whatever) during observation ... Why take the risk of having your eyeball(s)[fry] ... when you slip and remove the lens from the light path

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.

NASA Eclipse page:
umbra.nascom.nasa.gov/eclipse/ (http://umbra.nascom.nasa.gov/eclipse/)
August eclipse page:
umbra.nascom.nasa.gov/eclipse/990811/rp.html (http://umbra.nascom.nasa.gov/eclipse/990811/rp.html)
Eye Safety article:
umbra.nascom.nasa.gov/eclipse/990811/text/eye-safety.html (http://umbra.nascom.nasa.gov/eclipse/990811/text/eye-safety.html)
Chart of filter spectral responses:
umbra.nascom.nasa.gov/eclipse/990811/figures/figure_24.gif (http://umbra.nascom.nasa.gov/eclipse/990811/figures/figure_24.gif)

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.

One more tidbit, a direct quote from the above linked article on eye safety:

In spite of these precautions, the total phase of an eclipse can and should be viewed without any filters whatsoever. The
naked eye view of totality is not only completely safe, it is truly and overwhelmingly awe-inspiring!

[TheIncredibleHolg]

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!

[manhattan]

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:

1) 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?

2) 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.

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This is not an offer to agree or disagree with opinions, which may be done only by a current prospectus.

[falcon2]

Have there been any instances of mass blindness caused by awestruck people staring at an eclipsed sun?

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.


Do curious pets and livestock look up and suffer the consequenses?

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.