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Eclipse glasses
Eclipse glasses let you see a partial solar eclipse safely, but they have to come from a reputable dealer. (AAS / Evan Zucker Photo)

The country’s top astronomical organization says it’s alarmed by reports that potentially unsafe eclipse glasses are flooding the market in advance of the all-American solar eclipse on Aug. 21 – and in response, it has issued a list of approved manufacturers and vendors.

The flap already has sparked online battles between reviewers on Amazon’s website.

One dissatisfied “Verified Purchase” customer went so far as to post a picture that purportedly shows the glow of a 60-watt light bulb as seen through solar filters that were made in China.

“This would not be sufficient to protect your eyes from the sun,” the reviewer wrote in his one-star assessment. “I would never trust my eyesight to a pair of glasses from China.”

The  American Astronomical Society typically recommends looking for a label indicating that the glasses meet the ISO 12312-2 safety standard for direct viewing of the sun. But that’s “no longer sufficient,” the AAS said Tuesday in an updated advisory.

“It now appears that some companies are printing the ISO logo and certification label on fake eclipse glasses and handheld solar viewers made with materials that do not block enough of the sun’s ultraviolet, visible and infrared radiation to make them truly safe,” the advisory said. “Some sellers are even displaying fake test results on their websites to support their bogus claim of compliance with the ISO safety standard.”

To head off any concern, the AAS’ Solar Eclipse Task Force drew up a list of vendors that are considered reputable, inside and outside the U.S. The list includes 11 brands and dozens of vendors.

The free glasses that are being given out by libraries across the country (including Seattle Public Library) and by Astronomers Without Borders are also good to go, the AAS says.

“If we don’t list a supplier, that doesn’t mean their products are unsafe,” said Rick Feinberg, the AAS’ chief press officer and task force representative. “It just means that we have no knowledge of them or that we haven’t convinced ourselves they’re safe.”

There are a couple of easy ways to check your own solar glasses: Virtually the only thing you should be able to see through a safe solar filter is the sun itself. If you can see ordinary household lights through the filter, “it’s no good,” the AAS says.

Looking at the sun through the filter should produce an image that’s comfortably bright, like the full moon as seen by the naked eye. (Yes, you can look at the sun anytime through a safe solar filter.) If the sun’s image is uncomfortably bright, out of focus or surrounded by a murky haze, the “no-good” verdict applies.

If you suspect the glasses you bought aren’t unsafe, return them to the seller for a refund – and grab a good pair from one of AAS’ recommended vendors.

Eye protection will be needed to gaze at the sun during the partial phase of the Aug. 21 solar eclipse, which will be visible throughout North America. Even though the partially covered sun may not be as bright as full sun, its rays can be just as damaging to your retina. (But if you’re not interested in sun-gazing, you can forget about the glasses and go about your business.)

No glasses handy? You can monitor the eclipse’s progress by using a pinhole projection device that can be as simple as your own fingers, latticed together. NASA is even offering printable templates for classier-looking pinhole projectors. Be sure you look at the projected image on a wall or a sidewalk, rather than looking at the sun directly.

If you’re using a telescope or binoculars to observe the partial eclipse, put a solar filter designed for your viewing equipment in front of the primary lens (or lenses).

The same goes for your camera. Attach a filter that’s made for solar viewing on the lens, and don’t look at the sun directly through the viewfinder. Use the LCD viewscreen instead.

NASA has drawn up special instructions for taking photographs with your smartphone. Whether you’re using a smartphone or fancier equipment, it generally works better to have your camera mounted on a tripod. Set it up so that you minimize the jiggling when you click the shutter – for example, by using the camera’s time-delay feature.

There’s one time when you should dispense with the filters: during the eclipse’s total phase, which can be seen for only a couple of minutes within a 70-mile-wide track that stretches from coast to coast.

If you’re planning to take pictures during totality, you may want to rehearse in advance. To get ready, study this eclipse photography guide, written by NASA astronomer Fred Espenak.

Whatever you do, take some time to gaze at the blacked-out sun with your own eyes. Don’t get so hung up with f-stops and exposure times that you miss out on North America’s first taste of totality since 1979. And don’t become so beguiled by the sight that you forget to put your protective glasses back on when the total phase ends.

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