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Solar-Eclipse Glasses On Amazon May Not Meet NASA's Safety Requirements (qz.com)
For those planning to watch the solar eclipse on August 21st, you're going to want to make sure you have some specialized, ultra-dark glasses to see safely, especially if you're not in the "path of totality." If you're on the hunt for said glasses, please be on the lookout to make sure you buy glasses that meet NASA's safety standards. Quartz is reporting that there are many "fly-by-night manufacturers looking to turn a quick profit by selling subpar and potentially dangerous goods to unsuspecting Americans." From the report: The first stop for most seeking a pair of eclipse glasses is likely to be Amazon, where there are literally thousands of listings for the devices, ranging in materials from cardboard to bronze. I, too, went on Amazon to scout out a pair. I picked more or less at random: I chose a cheap pack of 10 cardboard glasses with five different designs, at least two of which were not garishly jingoistic. About a week after I bought them, I had a thought: Maybe I should double-check to make sure they met safety standards set by the scientific community. Next stop: NASA. NASA, of course, has a website dedicated to the 2017 eclipse, and on it, they have a section dedicated to eclipse-viewing safety. The site says that eclipse-viewing glasses must meet a few basic criteria: Have ISO 12312-2 certification (that is, having been certified as passing a particular set of tests set forth by the International Organization of Standardization); Have the manufacturer's name and address printed somewhere on the product; Not be older than three years, or have scratched or wrinkled lenses.
You only have one set of eyes, don't be foolish about this.
Chances are that non-certified stuff has deficiencies in UV/IR filtering, so while you may be able to look into the sun for much longer than usual, your eyes still may get an unhealthy dose of radiation. No protection at all will at least have you turn away in time (unless you're foolish enough to look at the sun through an unprotected telescope, binoculars or tele lens).
As an amateur astronomer, I use Baader visual solar filter film, adapted to my different scopes and lenses. An A4 sheet (you could make a load of sunglasses from this) comes at 25EUR, which is very cheap compared to other options for observing the sun. Most of all, it's safe!
Looking at the sun hurts. People glance and look away.
Looking at the sun through a bad filter that does not block UV does not hurt. People look and keep on looking. Then days, weeks or months later they find they have huge blind spots in their vision which spread outward over time and far to often are permanent.
Please, be careful with your incomplete advice.
kartune85 : Incapable of reason, observation or learning. A kind of dim, drab, flightless parrot.
Do not do either of these.
A floppy disk has only marginal IR protection, and blurs the image heavily.
Soot works if you deposit it at the right thickness, but it's easy to get the thickness wrong, and the slightest smudge can eliminate your protection; the coating is very fragile.
A common third trick is looking through CDs. Which can work, if you pick the right one, but their transparency varies dramatically, so there's no guarantee that an arbitrary one will offer sufficient protection. If you're willing to risk your eyes with an improvised filter, a CD should be good if you can barely see an incandescent bulb through it.
Photography filters and photographic film should never be used for looking at the sun. They don't block nearly enough IR.
More info about various homemade and professional filters tested here.
So, apart from that, how was the play, Mrs. Lincoln?
Yes a piece of welding glass works great but make sure you use at least a #14 glass per NASA recommendations. This is widely available through welding supply companies. Not all welding eye protection is adequate for looking at the Sun.
And for anyone using telescopes, binoculars or slr cameras...
Set a loud damn alarm for ten seconds before the end of totality, and do not leave unfiltered devices on tripods pointed at the sun. At best you'll wreck your camera. At worst some idiot kids (or adult) will try to sneak a peek.
I've seen the eyepiece cover of a Celestron kids telescope melt fully into the eyepiece itself on a scope left mounted after totality in China 2009.
kartune85 : Incapable of reason, observation or learning. A kind of dim, drab, flightless parrot.
Right. Cardboard box viewers make the image of the sun easier to see, because your eyes are in the dark box. But if you don't want to make a cardboard box viewer, you can do this: Cut a piece of aluminum foil (or thick paper), about 5 by 5 inches. Using a needle or a pin, punch a hole in the aluminum foil. Then grab the foil and a piece of white paper (maybe a sheet of computer paper), and go outside. Hold the foil a few inches over the white paper. The crescent will be projected onto the paper.
If you want to impress your kids, punch lots of holes, of varying diameters, into the foil. Then instead of projecting the "sun crescents" onto the paper, project them onto the sidewalk where your kids can see them. They will say, "Ooh, cool!"
4 bucks at Northern tool for just the glass, 4 bucks for welding goggles at Harbor Freight or 5 bucks for a flimsy paper pair of glasses. Going with the welding goggles.
And can re-use them later as a Steampunk Costume Prop. . .