Eclipse viewing is considered taboo in many indigenous cultures, most notably among the Navajo in the U.S., since the path of the May 20 annular eclipse falls directly across the tribe’s reservation. Although the taboo is spiritual, the dangers of looking directly at the sun, even during an eclipse, are well known.
Permanent eye damage can result if one looks directly at a solar eclipse, unless the entire disk is obscured during a total eclipse. This includes viewing through a camera, binoculars or a telescope, says the website MrEclipse.com.
“Staring at the sun under such circumstances is like using a magnifying glass to focus sunlight onto tinder,” the website says. “The retina is delicate and irreplaceable. There is little or nothing a retinal surgeon will be able to do to help you. Never look at the sun outside of the total phase of an eclipse unless you have adequate eye protection.
“Once the sun is entirely eclipsed, however, its bright surface is hidden from view and it is completely safe to look directly at the totally eclipsed Sun without any filters,” Mr. Eclipse says. “In fact, it is one of the greatest sights in nature.”
That window only lasts a couple of minutes, so it is only safe for an extremely short period of time. The annular eclipse that is happening on May 20 is not a total eclipse, however, so all precautions are necessary.
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Experts have devised several ways for people to see the effect safely, though, ranging from filters to artfully cut-out pieces of paper that project the phenomena onto the ground. Below is a description of various methods. And if you are not in the path of the eclipse—a 186-mile-wide track that in the U.S. will run diagonally through portions of eight states, from northern California to west Texas, cutting right through the Navajo reservation and elsewhere in Indian country—you can still watch it online with the Slooh Space Camera, which will livestream the event from telescopes in Japan, California, Arizona and New Mexico beginning at 5:30 p.m. Eastern Daylight Time, or 21:30 Greenwich Mean Time (GMT).
The Perkins Observatory and many other websites list safe ways to view an eclipse. All of them emphasize that all filters must be checked for pinholes before use, lest the sun creep in and harm one’s eye. Any filter with even a pinhole should be destroyed, Perkins says.
The most basic method, the pinhole camera, can be used to view the eclipse by projecting the shadow of it on the ground, thus looking down at your feet to see the heavenly event. It may result ina “small, dim and disappointing” image but it will preserve your eyesight if the other methods aren’t at your disposal. Instructions for making a pinhole camera are available for download here.
As for other, more direct methods, eclipse glasses are readily available, if one buys before supplies run out. (The Griffith Observatory in California, for instance, had already run out of them on Saturday May 19, the Los Angeles Times reported, as had several other venues.)
Eclipse glasses are generally made of a cardboard frame with two pieces of filtering material in lieu of bona fide lenses. These filters block out 99.9 percent of the sun’s visible light and 100 percent of the harmful ultraviolet (UV) rays, Perkins says on its website. The newer ones are better, made of black polymer lenses, while the older version has aluminized Mylar and are also good, the site says. You can also keep them on hand for sunspots and other solar events, such as the transit of Venus happening in early June.
Telescope filters are another method, if you have a telescope. They too filter out most of the sun’s light. These of course only work on an actual telescope, which many of us do not have. Older eyepiece-style solar filters tend to crack under the sun’s heat, Perkins says, so they are not considered reliable and should not be used.
One type of welder’s glasses, number 14 (the darkest), is enough to block out the sun’s brightness so that you can view the eclipse safely, Perkins said. But the effect is not cumulative, i.e. you cannot reach 14 by putting two sevens together (the numbering starts at one and ends at 14).
Telescopic projection gives a “nice, large, bright image visible to several people at the same time,” Perkins said, requiring nothing more than a telescope and a flat screen. “HOWEVER: It can be VERY DANGEROUS unless one knows EXACTLY how to do it properly! Not only can it cause severe and permanent eye damage, but it can also easily set things on fire. USE CAUTION when following these instructions!”
If you don’t want to view alone, or aren’t sure of how to do it safely, many places will be holding eclipse parties and viewing opportunities through telescopes. Those of us not in the path of even a partial eclipse—the U.S. Northeast, for example, will already be in darkness when the eclipse happens so will see nothing—can view it online from Japan, China and other countries starting at 5:30 p.m. Eastern Daylight Time at the SLOOH space cam.
Here’s a video on how to build a pinhole camera, the lowest-tech and easiest available eclipse-viewing method, from a shoebox. Although even lower tech, according to NASA, you can interlace your fingers waffle-style, hold them under the sunlight and look down to see the eclipse’s shape on the ground. In the case of the partial eclipse, the shadows will be crescent-shaped.
The story was originally published on May 21, 2012.