Be Safe, Get The Right Filter To View The Solar Eclipse

A student looks at the partially eclipsed sun in northern England on March 20, 2015. Credit: Reuters

There’s a good chance that more people on Earth will witness the August 21 total solar eclipse than any other eclipse in history. Many will share in the sight thanks to a flood of eclipse glasses available free or through a myriad of online outlets. But as in any endeavor to lift people up, there’s always a fringe element working hard to figure out ways to cheat the system and profit. The latest scam is fake eclipse glasses. These are eclipse shades that aren’t up to specs and allow dangerous visible, infrared and ultraviolet light into your eyes, where it can damage your retinas.

You used to be able to look for the logo of the International Organization for Standardization (ISO) on filters indicating that it meets the ISO 12312-2 international safety standard for filter for direct viewing of the sun. Even that may not safe anymore because certain outfits are printing that on the product even when it doesn’t meet the standard. Fortunately, there are a couple sure fire ways you can verify you have safe eclipse glasses or hand-held filters.

There are lots of ways to view the eclipsed sun indirectly. One of the most creative is simply to take along a colander. The individual openings in the mesh act like pinhole lenses and will project tiny images of the sun. Credit: Reuters

Libraries across the U.S. will be handing out 2 million pairs of free eclipse glasses. Those plus any glasses from a planetarium, science museum or astronomy trade show comply with standards and are safe. Major suppliers such as Rainbow Symphony, Thousand Oaks, B&H Photo, Walmart, 7-Eleven and MANY others are perfectly fine. Just be careful going online and grabbing a pair from someone NOT on the American Astronomical Society’s (AAS) list of Reputable Vendors of Solar & Viewers.

A child looks at pinhole projections produced as sunlight passes through a card punched with small holes using a pin, during an eclipse at Taipei Astronomical Museum May 21, 2012. The Chinese characters read, “Taipei.” Credit: Reuters/Pichi Chuang

To be fair, just because a business isn’t listed doesn’t necessarily mean their filters are unsafe, simply that the AAS has no knowledge of them and can’t vouch for that outlet meeting standards. Remember that you can also buy a safe #14 welding glass filter from a welding supply company, but make sure it’s a #14. Don’t get a #13 if they’re out of #14s!

A #14 welders glass is the perfect tool for naked eye sunspot viewing. This glass gives a green image (near center) of the Sun. Credit: Bob King

You can also check your filter to be sure it’s doing its job. A compliant solar filter will show the sun surrounded by a dark sky. It will also show the interior or filament of a bright light bulb or LED if you get right on top of it. (I’ve tried this with my own safe filters). You shouldn’t be able to just look through a filter and see ordinary household lights. If you do, send it back for a refund.

OMG, don’t do this! Bridal pair Sarah Wolf and Michael Wilde (right) and their guests look through a rescue foil as they watch a partial solar eclipse in Munich, Germany, March 20, 2015. Credit: Reuters

So what does happen if you stare at the sun? Will you go blind? We have a built-in aversion to looking directly at the sun. I can’t even imagine doing it. Direct sunlight overloads the retina with light, causing it to release chemicals that can damage it. Unlike grabbing a hot pot bare-handed, where you instantly feel the back and withdraw, most of us don’t sense pain in our retinas, making looking at the sun even more dangerous.

Small gaps along the length of this palm leaf acted as “pinhole lenses” to project a series of solar crescents on the ground during the July 1991 eclipse. Credit: Bob King

Medical journals record instances of retinal damage via sunlight called solar retinopathy. For some, vision returns to normal after several months. Others see a ghostly crescent (from the crescent sun) floating in their vision for years. English astronomer Thomas Harriot, who studied sunspots in 1610, reported that his “sight was dim for an houre” after solar observations. Isaac Newton nearly lost his vision for three days after trying to provoke afterimages, those dark shapes you see when someone pops a camera flash in your eyes, by staring at the sun in a mirror. He got afterimages alright … for months! Newton’s vision eventually recovered.

A final note. You’ll need a filter if you’re observing the sun at any time other than when it’s totality eclipsed by the moon. That’s easy to remember. During totality you can remove it and take in the spectacle.

You can also view the sun indirectly under a leafy tree — the tiny gaps between the leaves act as pinhole lens projectors and will beam a blizzard of tiny solar crescents on the ground below. Or you can project a crescent sun through the little hole in your almost-clenched fist onto a piece of paper.

There are lots of safe ways to enjoy an eclipse.

6 Responses

      1. Edward M. Boll

        I clicked the link and the only thing that came up was optim. Maybe, I will have to try a different computer. We also bought some at Homestead National Monument where we plane to be for the event. I hope that these are safe. NASA will be there.

        1. astrobob

          Hi Edward,
          I checked the link and it’s good, so I’m not sure what’s up on your end. I’m sure ones from a national monument will be fine. I hope you have clear skies on the big day!

    1. astrobob

      Wow – incredible. No wonder there are fake filters out there. I still have a bunch and our library’s giving them away for free on eclipse day.

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