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How to view the eclipse safely
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On Aug. 21, Americans will be able to observe a total eclipse for 2 to 3 hours in an approximately 70-mile-wide zone stretching from the Northwest to the Southeast.
“A total solar eclipse is always very dramatic,” Carlton “Tad” Pryor, a professor in the department of physics and astronomy at Rutgers University-New Brunswick, said in a press release from Rutgers University.
He said that anyone wishing to see the phenomenon must protect their eyes with specially made and certified filters, or by observing the eclipse indirectly.
Direct viewing can be done safely with no. 14 arc welder glass or with eclipse viewing glasses that meet the following criteria outlined by NASA:
Have certification information with a designated ISO 12312-2 international standard;
Have the manufacturer’s name and address printed on the product; and
Not be used if more than 3 years old or with scratched or wrinkled lenses.
Homemade filters or sunglasses, even very dark ones, are never safe for looking directly at the sun, according to the release.
While it is safe for those in the path of totality to look at the sun without special glasses during the very brief total eclipse period, at no other time or in areas outside of the totality path is it safe to view without ISO-approved glasses, according to Lorne Yudcovitch, OD, in a press release from The Pacific University College of Optometry.
There are reports of potentially unsafe eclipse glasses appearing for sale, so be sure to buy eclipse viewers from reputable vendors, he said.
Most retinal damage from the sun comes from the visible spectrum light and some infrared light, both of which have longer wavelengths than ultraviolet light that can be filtered by conventional sunglasses, Yudcovitch said.
“Conventional glasses, even very dark ones, are nowhere near as dark as what is needed to stare at the sun directly, even during a partial eclipse when 99% of the sun is eclipsed by the moon,” he stated.
Solar retinopathy entails photochemical damage to the retinal cells, Yudcovitch said.
It occurs when sunlight burns and potentially scars the retina, according to a press release from the NEI. Symptoms of solar retinopathy include central graying and fuzziness of vision.
“This damage can occur without feeling pain because the human retina has no pain receptors,” Yudcovitch said. “So, looking at the sun even when it is mostly but not entirely ‘covered’ by the moon without glasses could be damaging your eyes because you might not be as sensitive to the light exposure as you would when looking at a completely unobstructed sun.”
There is no cure for solar retinopathy, so prevention is critical, he added.
He also does not recommend viewing the eclipse through the lenses of telescopes, binoculars or camera viewfinders, even with the proper use of a solar filter in front of the camera or scope lens. The lenses may magnify the sun’s rays on the retina many more times than usual, even when wearing special solar glasses.
Pryor presented options for safe, indirect viewing. If the sky is clear on the day of the eclipse, stand in a leafy tree’s shadow and look at the ground. The smallest spots of sunlight will make small crescent shapes, showing the sun’s apparent shape as the moon crosses in front.
Another method is to make a small hole in a piece of cardboard with the tip of a pencil or pen and project the light onto a white piece of paper, he said. For a better view, put the hole over a mirror and reflect the light onto a more distant white piece of paper or white surface.
References: nei.nih.gov, pacificu.edu, rutgers.edu