You managed to score a pair of those highly coveted eclipse glasses, and the moment is almost here. But how can you be absolutely certain they'll do their job and protect your eyes?
It's simple: You need to check them. If you have legit glasses-- and not fakes, like the ones Amazon recalled earlier this week-- you shouldn't be able to see ANYTHING but the sun. As in, nothing. No lights. Nothing. So just because they're labeled "ISO 12312-2" doesn't mean they're going to work.
According to the American Astronomical Society, safe solar filters produce a view of the sun that is comfortably bright-- like the full moon. It's in focus and surrounded by the dark sky. If you look through your eclipse glasses and find the sun to be uncomfortably bright, out of focus or surrounded by a bright haze, they're no good.
Here's how to check your eclipse glasses:
FOX 5's Sue Palka says you need to give your glasses a test run. Before the eclipse, head outside Sunday night as the sky starts to get dark (similar to what will happen on Monday afternoon). Look up at a street light. You should NOT be able to see it. If you can, those glasses aren't doing their job and you shouldn't use them during the eclipse .
The American Astronomical Society says you shouldn't be able to see anything through a safe solar filter or eclipse glasses EXCEPT the sun, or something that is comparably bright-- including the sun reflected in a mirror, a sunglint off shiny metal, the hot filament of an unfrosted incandescent light bulb, a bright halogen light bulb, a bright-white LED bulb (including the flashlight on your smartphone), a bare compact fluorescent (CFL) bulb, or an arc-welding torch. All of these sources of light (except maybe the welding torch) should be very dim when viewed through a safe solar viewer or pair of eclipse glasses.
If you can see shaded lamps or other common household light fixtures (this does not include bare light bulbs) of more ordinary brightness through your eclipse glasses or handheld solar viewer, and you're not sure the product came from a reputable vendor, it's no good.
The American Astronomical Society reminds you that a pair of genuinely safe glasses (or a solar viewer) does more than just reduce the level of the sun's brightness. It also blocks UV and IR radiation, which could be harmful. They say the only way to tell whether your viewer does that is to be certain that it meets the ISO 12312-2 safety standard, and the only way to know that is to be certain that it came from a reputable vendor.
Make sure you test your glasses before Monday, and if you're not sure, don't chance it! You can watch the eclipse with us all day long beginning at 11:30 am -- and that's guaranteed to be safe.