Those pesky eclipse glasses: Should you wear them?
The short answer is: Yes. Your eye health is important and you’ll want to play it safe.
But there is a lot to consider when it comes to safely viewing the Great American Eclipse on Aug. 21. Let’s dive in.
The 411 on the viewing glasses
It’s like we just said: If you’re going to be watching the eclipse directly, you’ll need eclipse glasses, at least, for most of the event. It all depends on whether you’ll be seeing totality, which we'll explain later. But yes: Buy the glasses either way. And make sure you check the safety authenticity, to ensure the glasses meet the basic proper viewing standards that NASA recommends on its website.
Eclipse glasses and hand-held solar viewers should meet all the following criteria:
-- Have certification information with a designated ISO 12312-2 international standard
-- Have the manufacturer’s name and address printed somewhere on the product
-- Not be used if they are more than three years old, or have scratched or wrinkled lenses
-- Viewers of the eclipse should not use homemade filters or ordinary sunglasses -- not even very dark ones -- because they are not safe for looking directly at the sun.
NASA’s partner, the American Astronomical Society, has verified five manufacturers that are making eclipse glasses and hand-held solar viewers that meet the ISO 12312-2 international standard. They are:
1.) American Paper Optics
2.) Baader Planetarium -- AstroSolar Silver/Gold film only
3.) Rainbow Symphony
4.) Thousand Oaks Optical
5.) TSE 17
NASA officials even created an easy-to-read flyer about how to tell if the glasses you’ve chosen are safe.
So let’s be clear: When exactly can I look, unprotected?
It’s a very short window, and it only applies to those who will be viewing totality. That’s why we said you needed the glasses either way.
Here’s the deal: It’s not ever safe to look directly at the sun’s rays, even if the sun is partly obscured. So if you’re not in the path of totality, and therefore, you’re watching a partial solar eclipse, you have to keep your eclipse glasses on -- or use an alternate indirect method -- at all times, if you want to face the sun.
It’s a similar situation during a total eclipse -- up until the time when the sun is completely blocked.
During the short time when the moon obscures the sun, known as the period of totality, it is safe to look directly at the star. Because it's blocked, right? Still, you need to be aware of when to take off your glasses and when to put them back on.
In a nutshell, you need the glasses. But if you’re viewing totality, don’t listen to the urban legends about “going blind” if you look without protection. When the moon is entirely blocking the sun’s bright face, on the contrary, that’s the only safe time you CAN look. Just remember, totality will only last for about two or 2 ½ minutes. As soon as the bright sun begins to reappear, put your solar viewer back on to glance at the remaining partial phases.
Are there any alternatives to the glasses?
You could try a pinhole projection if you want to see the partially eclipsed sun.
Here’s how you do it: Cross the outstretched, slightly open fingers of one hand over the outstretched, slightly open fingers of the other. With your back to the sun, look at your hands’ shadow on the ground. The little spaces between your fingers will project a grid of small images on the ground, showing the sun as a crescent during the partial phases of the eclipse.
Otherwise, the only safe way to look directly at the uneclipsed or partially eclipsed sun is through special-purpose solar filters, such as the eclipse glasses, or hand-held solar viewers. Homemade filters or ordinary sunglasses, even very dark ones, are not safe.
A few ground rules
-- Always inspect your solar filter before using it. If you find it’s scratched or damaged, don’t use it. Read and follow any instructions printed on or packaged with the filter. Always supervise children.
-- Stand still and cover your eyes with your eclipse glasses or solar viewer before looking up at the sun. After glancing at the sun, turn away and remove your filter. Don’t remove it while looking at the sun.
-- Do not look at the sun through an unfiltered camera, telescope, binoculars or other optical device. Similarly, do not look at the sun through a camera, a telescope, binoculars or any other optical device while using your eclipse glasses or hand-held solar viewer. The concentrated solar rays will damage the filter and enter your eyes, causing injury.
Why are we talking about this?
In case you’re feeling out of the loop, we’ll explain quickly. On Aug. 21, the whole continent will experience a partial solar eclipse. It’s expected to last two to three hours. Halfway through, anyone who happens to be in the path of totality -- which is about 70 miles wide from Oregon to South Carolina -- will see a total solar eclipse. That means the moon will completely block the sun’s bright face for up to 2 minutes and 40 seconds, according to NASA. Of course, this is all weather permitting. But anyone who’s in an area that experiences totality is in for a treat.
NASA calls this “one of nature’s most awesome sights.” Bright stars and planets will be visible. Day will be turned into night. The otherwise-hidden solar corona, which is the sun's outer atmosphere, will be made visible. And it’s pretty rare for this to happen on such accessible ground. Total solar eclipses happen every year or two, but many occur over the oceans or in remote areas where not as many people are able to watch. And now you know.
Information and tips: NASA