If you're planning to watch the solar eclipse that will sweep across the nation on August 21, you're probably looking for some eye protection. After all, gazing at a solar eclipse with the naked eye — even if you're not in the so-called path of totality — can harm your vision, perhaps permanently.
The good news? Eclipse-viewing glasses will be pretty easy to come by in the weeks leading up to the long-anticipated celestial event. From public libraries to museums and hotels to eyewear retailers, all sorts of organizations are handing out free eclipse glasses. So keep your eyes peeled.
Your best bet might be your local library. More than two million eclipse glasses will be given out free of charge by over 7,000 public libraries across the U.S. To find out if a library near you is participating in the giveaway program, which is being mounted with help from the National Center for Interactive Learning, click on this link.
Other places you might be able to snag some free eclipse glasses include your public health department, local astronomical societies (if one is in your area), and planetariums. And eyewear retailer Warby Parker is giving away free eclipse glasses at each of its 44 locations.
If you can't find any freebies, various eclipse eyewear options — from simple cardboard-framed filters costing only a few dollars to expensive eclipse-safe binoculars and cameras — can be purchased from drugstores, grocery stores, and online retailers.
Wherever you get your glasses, make sure they're safe for eclipse viewing ("counterfeit" viewers have been reported). Look for glasses bearing the designation ISO 12312-2, along with the manufacturer's name and address. Avoid glasses that are more than three years old and those with scratched or wrinkled lenses.
Whether you're handy or not, don't even think about watching the eclipse through conventional sunglasses (even ones with very dark lenses). And forget about making eclipse eyewear a do-it-yourself project. Trying to make your own eclipse glasses out of tinted filters is a definite — and potentially dangerous — no-no.
"If somebody looks at the sun through such materials, they could incur a retinal injury and by the time they realize it the next day, it will be too late and nothing can be done," Dr. B. Ralph Chou, a retired professor of ophthalmology at the University of Waterloo in Ontario, Canada and a leading expert on eclipse safety, told NBC News MACH in an email.
If the eclipse comes and you find yourself without eye protection, make a pinhole projector and watch a projection of the eclipse on a blank white surface. All you need is a notecard, aluminum foil, tape, and a pin. And, of course, the sun.