Viewing the Great American Solar Eclipse of 2017--Safely
On August 21, 2017, a solar eclipse will be visible across a section the continental United States, coast to coast, for the first time since 1918.
A solar eclipse occurs when the Moon passes between the viewer on Earth and the sun, completely—and perfectly—blocking out the full diameter of the sun. During this event, if you are within the path of totality (the shadow of the eclipse), the sky darkens and you will be able to see the solar corona, the extended atmosphere of the sun made up of plasma and reaching millions of miles beyond the part of the sun that is normally invisible to us. This is, by all accounts, a spectacular and life-changing event. Anywhere else in the country, outside the path of this shadow, you will see partial phases of the eclipse. And while I’ve not yet personally seen one, I have nearly blinded myself observing the sun, so using precautions when viewing the eclipse is critical.
WHERE TO GO
If you plan on viewing the total eclipse, you will need to head to a part of the country where the 70-mile wide shadow will cross the continent. It will enter the US on the Oregon coast, then sweep across the country, exiting in South Carolina. A complete map of the eclipse path can be found here. NASA also has a website up for this event.
TIMING AND EXPERIENCE
If you are in the path of totality, the eclipse begins in Oregon at 10:15 Pacific Daylight
Time, and ends on the shores of South Carolina 94 minutes later. As the shadow approaches your location, you will see an increasingly large portion of the sun darkened by the mass of the Moon. A few moments before totality, you may see the shadow moving towards you across the landscape from the west as it rapidly approaches at a speed of between 2400 mph in Oregon to 1500 mph in South Carolina. As totality begins, just before the sun is completely covered by the Moon, you will see bright points of light along the edge of the disk called “Baily’s Beads.” These are bits of sunlight skimming through valleys and crevices in the lunar surface, and last for just a few seconds. Then—totality. At the centerline of the Moon’s shadow, this phase will last for about two minutes, to two minutes, forty seconds, depending on your location. At this time, the sky will be dark as late twilight—animals will react to what they perceive as sunset, temperatures will drop, and wind may blow as the air mass around you becomes colder. The solar corona will be visible and brighter stars will appear. Steve Fentress, director of the Strasenburgh Planetarium in Rochester, New York, and author of the new astronomy book “Sky to Space,” says that there will be other things to look at during this time: “During totality in this eclipse, the sky should become dark enough for Jupiter to be seen off to the Sun's lower left and Venus to the upper right.” Both will add to the spectacle.
Then, just as it began, the Baily’s Beads will appear on the opposite side of the lunar disk, and the sun will gradually emerge, moving into partial phases again. Then the large crowds will begin their long journey home, through massive traffic jams and throngs of exhausted but overjoyed eclipse-watchers.
A clever wag in Bend, Oregon appears to have coined the term “apocaclypse” for what is expected to be a massive short-term migration of people to the path of totality a day or so before the 21st. Most of the regions within the path are rural and served by two-lane highways at best, so traffic will snarl on the morning of the event, and local services will be strained. Emergency responders will likely not be able to get to people in need, food will be hard to come by, and even budget motels are already charging upwards of ten times their normal prices—hence the “apocaclypse.” Be sure to bring food, water, and any medical supplies you may need, and be prepared to spend many hours getting in and especially out of the area—it will be like a Beatles reunion (or ten Comic-Cons, depending on your generation) regarding traffic flow. Be prepared.
VIEWING THE ECLIPSE
This cannot be stressed enough: be smart and view the eclipse safely! Even short glances at the sun can cause permanent eye damage. Remember how kids used to burn ants under a magnifying glass? That’s exactly what the lenses in your eye will do to your retina if you get a shaft of direct sunlight shining into your unprotected eye for more then a moment.
PARTIAL PHASE VIEWING CAUTIONS
To observe any phase of the eclipse before or after totality—and even right on the verge of it—you need certified eye protection. There are hundreds of vendors all over the country and online selling “eclipse glasses” and “eclipse viewers”… but be wary. You must be sure that the viewing device you buy is rated for safety by the International Standards Organization, also known as ISO. Their rating, which must be printed on the viewing device, should read “ISO 12312-2.” This means that the viewing medium is properly made to block all harmful solar radiation and can be used to safely view the sun anytime. But there are many unscrupulous parties out there making fake knockoffs with cheaper materials, and some even have the ISO certification falsely printed on them. How can you make sure you are getting the real deal?
The only way to be sure that you are protecting your eyes, and those of your family, is to buy your viewing device from a reputable source. Some of the safe manufacturers are:
Ideally, you will have time to buy yours directly from the manufacturer from their website, if available. But most of us will go to a store or website to purchase. Retail outlets said to be reliable by the American Astronomical Society include:
Some reputable online outlets suggested by the same organization are:
Astronomical Society of the Pacific
Discover Magazine’s My Science Shop
Sky & Telescope’s online store
Then, there is the question of buying through Amazon. A search for “eclipse glasses” at Amazon turns up a bewildering array of devices that may or may not be safe to use, though most of the vendors make pains to suggest that they are. Proceed with caution. Make sure that the device you buy is manufactured by a recognized supplier, is ISO certified, and brand new (they can degrade over time and with use). Also, to be extra sure, check that the devices are coming directly from that manufacturer and being fulfilled by Amazon—otherwise, you have no idea what you will actually receive. Amazon is said to be doing what they can to protect consumers, but the traffic at the company is simply too great for them to catch all offenders. The same is true for Walmart’s online site and those of other general retailers--third party vendors are selling dangerous imitations. Don’t take chances—you don’t want your children staring at the sun through a viewer that can damage their vision.
FREE AND (PRESUMABLY) SAFE
Many public libraries and science museums are giving away free viewers, and these are presumed to be safe to use. But when you receive your viewers, check them— the sun should appear fairly dim, with no lines or bright spots, and it should not irritate your eyes at all to use them. If this is not the case, toss them and find another. Also, if the viewing surface is creased or scratched, do not use them. Go find another, unblemished pair. And if you have bought safe, certified cardboard viewers, don’t put them in a pocket where they may get folded or creased—the mylar surfaces need to be kept flat and non-abraded. This is especially relevant for children, who will put just about anything given them into a hip pocket. Keep the viewers in hand until you’re ready to supervise their viewing of the sun.
Again, you should see a dim, yellow/brown disk of the sun—nothing more. Note that even if your eyes are being damaged by inadequate viewers, you will not feel it--you will not nothing until vision begins to fade in a day or two. Be careful.
ALTERNATIVE VIEWING DEVICES
The safest and most foolproof way to view a partial phase of the eclipse is with a pinhole projector. These are easy to make and absolutely safe if used properly. Take a box lid or paper plate and punch a hole through it with a small nail. Then take a second paper plate or piece of cardboard and hold or mount it about 18-24 inches from the pinhole. Angle the apparatus so that the pinholed sheet is perpendicular with the light from the sun, and you will see a small image of the solar disk projected onto the second sheet. This is not an image of the hole, but an optical reproduction of the sun’s disk. Do not look at the sun through the pinhole! This common misperception of how pinhole projectors work has caused eye damage to many. This device is for projection only. Practice with it before the day of the eclipse so you’re not fiddling around at the last moment—it takes some getting used to.
Finally, there are solar filters being sold for telescopes. These should also be ISO rated, and attach only to the forward end of the telescope—don’t use an eyepiece-mounted filter! They can crack, and in that instant, you will be blinded. Many of these are also knock-offs and unsafe, be be cautious when shopping. The same rules apply as when buying viewers.
You can view the eclipse in its partial phases from anywhere in the continental US. Many people will be drawn to public viewing events, which is great—it’s more fun when shared. But again, be careful what devices you use. If someone is handing out free viewers, make sure they are ISO compliant. And even if they are, since you do not now the source, use them sparingly, for short glances only.
If someone has set up a sun projector, that’s great—enjoy it. If they have a telescope with a solar filter, there is no guarantee that it’s safe to use—you’re taking the chance that he or she bought something sub-par, and it’s not worth the risk.
Fentress has this to say about the use of telescopes—yours or those belonging to others— during an eclipse. “If you don't already know exactly what you are doing, this is not the time to learn how to select and use a solar attachment for a telescope. Most people can't get a telescope pointed at the Moon without help; adding another device is too much to undertake on short notice. Go to eclipse party hosted by a science museum, university, or established adult astronomy club, where there are likely to be people who have properly configured telescopes and know how to use them.” It goes without saying that the small aiming scope on the side of most telescopes will also damage your eyes if you attempt to use it, even briefly, to aim the instrument.
During the phase of totality—when the sun is completely covered by the Moon—you may view the eclipse with the naked eye and even binoculars. But you must be certain to wait until totality and to stop well before the end of totality—sunlight emerging past the Moon’s disk will be magnified and can damage your eyes.
A PERSONAL WARNING, FROM EXPERIENCE
Seeing a total solar eclipse is said to be an astounding event. Viewing the partial phases is exciting. But neither is worth risking your eyesight. It may seem that I am being overly cautious, but it’s all too easy to let a moment of temptation lead to a permanent disability.
When I was a young boy in the 1960s, my father bought me an inexpensive telescope that included a solar filter you could screw into the eyepiece. There was a warning printed on the filter to use only for brief periods, but what 8-year old follows such instructions? I used the device frequently for a couple of years without adult supervision. By my mid-40s, I was beginning to have vision trouble with my right eye—the same eye I used for viewing the sun. By 55 I had moderately severe cataracts, with about 40% vision loss. I had to have the lenses in both eyes replaced. When I got my final exam before the surgery, the eye doctor called his staff into the examination room to witness the youngest person with pronounced cataracts he had ever seen. They were fascinated—I was not. We agreed that the damage was from a combination of growing up in a sunny climate (southern California) and very probably the use of that telescope for observing the sun. And had that little screw-in filter cracked during use—they get very hot—I would have been instantly blinded by 50 power magnification of direct sunlight.
Other people have similar stories, but they all end with the same result—some kind of eye damage. It doesn’t seem all that serious until your vision begins to grey-out, lose focus and dim, then it really gets your attention. In the end, it all comes down to one point: play safe with your eyes, and supervise your children while viewing any part of the eclipse. Feel free to advise friends and neighbors if you perceive them viewing in an unsafe manner—they may or may not thank you later, but you will be doing them a favor.
The Great American Solar Eclipse—or apocaclypse—is coming up shortly. Be prepared and enjoy one of nature’s greatest spectacles safely.
Safe Viewing Devices and Reputable Sellers
Griffith Observatory’s Eclipse Page