ATLANTA -- As businesses around the United States find different ways to cash-in on the upcoming total solar eclipse, experts are warning that not all eclipse glasses being sold are what they seem.
The American Astronomical Society reports that sky-watchers need to be mindful of the glasses that are now flooding the market since not all will protect human eyes from the effects of the celestial event.
"We used to say that you should look for evidence that they comply with the ISO 12312-2 international safety standard for filters for direct viewing of the Sun," the organization posted on its website. "But now the marketplace is being flooded by counterfeit eclipse glasses that are labeled as if they're ISO-compliant when in fact they are not."
That means that even the ones that are marked as compliant could be fake. Viewers who end up with fake glasses could run the risk of getting a condition known as "eclipse blindness" or serious damage to the retina.
"Filters that are ISO 12312-2 compliant not only reduce visible sunlight to safe and comfortable levels but also block solar UV and IR radiation," officials said.
Only five of those exist - American Paper Optics, Baader Planetarium (AstroSolar Silver/Gold film only), Rainbow Symphony, Thousand Oaks Optical and TSE 17.
If you decide to buy eclipse glasses elsewhere, there are ways to spot a fake. For one, the AAS reports that these glasses will only allow in light from the sun. So if you can see household light, they won't protect you. The filters are also designed to let through enough light to view the event comfortably. So if it seems too bright, it probably is.
They also recommend that you avoid some of the more recent homemade alternatives that are popping up online.
"Dark sunglasses (or multiple pairs of sunglasses), neutral density or polarizing filters (such as those made for camera lenses), smoked glass, exposed film, 'space blankets,' potato-chip bags, DVDs, and any other materials you may have heard about for solar viewing are not safe," the organization posted.
They pointed out that even if they may dim the effects of the Sun, they don't necessarily protect the eyes from other parts of the electromagnetic spectrum.
"While enjoying a 'comfortable' view of the 'dim' Sun, solar infrared radiation could be cooking your retinas. And you wouldn't know till later because your retinas don't have pain receptors," the organization states.
The one "homemade" viewers that might work are welding filters - but even then only those at shades of 12, 13 or 14 which is much darker than what most welders actually use.
The good news with getting legitimate certified eclipse glasses is that the latest standard leaves behind some of the precautions that existed with older ones.
If they are ISO 12312-2 compliant, they can be reused - even after three years - as long as they aren't scratched or damaged. They also allow viewers to look at the sun for an unlimited amount of time. Previous glasses warned that users could only view the sun for 3 minutes at a time.