On August 21, 2017, millions of people across the United States will see nature's most wondrous spectacle — a total eclipse of the Sun. It is a scene of unimaginable beauty; the Moon completely blocks the Sun, daytime becomes a deep twilight, and the Sun’s corona shimmers in the darkened sky. This is your guide to understand, prepare for, and view this rare celestial event.
Facts you should know about the August 21, 2017, total solar eclipse
This will be the first total solar eclipse in the continental U.S. in 38 years. The last one occurred February 26, 1979. Unfortunately, not many people saw it because it clipped just five states in the Northwest and the weather for the most part was bleak. Before that one, you have to go back to March 7, 1970.
A solar eclipse is a lineup of the Sun, the Moon, and Earth. The Moon, directly between the Sun and Earth, casts a shadow on our planet. If you’re in the dark part of that shadow (the umbra), you’ll see a total eclipse. If you’re in the light part (the penumbra), you’ll see a partial eclipse.
A solar eclipse happens at New Moon. The Moon has to be between the Sun and Earth for a solar eclipse to occur. The only lunar phase when that happens is New Moon.
Eclipse totalities are different lengths. The reason the total phases of solar eclipses vary in time is because Earth is not always at the same distance from the Sun and the Moon is not always the same distance from Earth. The Earth-Sun distance varies by 3 percent and the Moon-Earth distance by 12 percent. The result is that the Moon’s apparent diameter can range from 7 percent larger to 10 percent smaller than the Sun.
You want to be on the center line. This probably isn’t a revelation, but the Moon’s shadow is round. If it were square, it wouldn’t matter where you viewed totality. People across its width would experience the same duration of darkness. The shadow is round, however, so the longest eclipse occurs at its center line because that’s where you’ll experience the Moon’s shadow’s full width.
The center line crosses through 10 states. After a great west-to-east path across Oregon, the center line takes roughly nine minutes to cross a wide swath of Idaho, entering the western part of the state just before 11:25 a.m. MDT and leaving just before 11:37 a.m. MDT. Next up is Wyoming, where the umbral center line dwells until just past 11:49 a.m. MDT. The center line hits the very northeastern part of Kansas at 1:04 p.m. CDT and enters Missouri a scant two minutes later. At 1:19, the shadow’s midpoint crosses the Mississippi River, which at that location is the state border with Illinois. The center line leaves Illinois at its Ohio River border with Kentucky just past 1:24 p.m. CDT. Totality for that state starts there two minutes earlier and lasts until nearly 1:29 p.m. CDT. The center line crosses the border into Tennessee around 1:26 p.m. CDT. Then, just past the midpoint of that state, the time zone changes to Eastern. The very northeastern tip of Georgia encounters the center line from just past 2:35 p.m. EDT until not quite 2:39 p.m. EDT. Finally, it’s South Carolina’s turn. The last of the states the center line crosses sees its duration from 2:36 p.m. EDT to 2:39 p.m. EDT. One further note: The extreme northeast part of Georgia does experience some totality, but at no point does the center line pass through that state.
Totality lasts a maximum of 2 minutes and 40.2 seconds. That’s it. To experience that length, you’ll need to be slightly south of Carbondale, Illinois, in Giant City State Park. You might think about getting there early.
Cool things are afoot before and after totality. Although the big payoff is the exact lineup of the Sun, the Moon, and your location, keep your eyes open during the partial phases that lead up to and follow it. As you view the beginning through a safe solar filter, the universe will set your mind at ease when you see the Moon take the first notch out of the Sun’s disk. Around the three-quarters mark, you’ll start to notice that shadows are getting sharper. The reason is that the Sun’s disk is shrinking, literally approaching a point, and a smaller light source produces better-defined shadows. At about 85 percent coverage, someone you’re with will see Venus 34° west-northwest of the Sun. If any trees live at your site, you may see their leaves act like pinhole cameras as hundreds of crescent Suns appear in their shadows.
Totality is safe to look at. During the time the Moon’s disk covers that of the Sun, it’s safe to look at the eclipse. In fact, to experience the awesomeness of the event, you must look at the Sun without a filter during totality.
Yes, the Sun’s a lot bigger. Our daytime star’s diameter is approximately 400 times larger than that of the Moon. What a coincidence that it also lies roughly 400 times farther away. This means both disks appear to be the same size.
You won’t need a telescope. One of the great things about the total phase of a solar eclipse is that it looks best to naked eyes. The sight of the corona surrounding the Moon’s black disk in a darkened sky is unforgettable. That said, binoculars give you a close-up view — but still at relatively low power — that you should take advantage of several times during the event.
Nature will take heed. Depending on your surroundings, as totality nears you may experience strange things. Look. You’ll notice a resemblance to the onset of night, though not exactly. Areas much lighter than the sky near the Sun lie all around the horizon. Shadows look different. Listen. Usually, any breeze will dissipate and birds (many of whom will come in to roost) will stop chirping. It is quiet. Feel. A 10°–15° F drop in temperature is not unusual. ~ from Astronomy Magazine
Get a filter in advance
Cardboard “eclipse” glasses with lenses of optical Mylar cost about $2. Such a device — it’s not a toy — will let you safely look directly at the Sun. It filters out most of the light, all of the dangerous infrared (heat) and ultraviolet radiation, which tans our skin. ~ Contact the Bonne Terre Airport, they are selling glasses, as are our friends at the Park Hills Chamber of Commerce.
Bring a chair
In all likelihood, you’ll be at your viewing site several hours before the eclipse starts.
Don’t forget the sunscreen
Most people who go outside during the summer know this. Remember, you’ll be standing around or sitting outside for hours. You may want to bring an umbrella for some welcome shade.
Take lots of pictures
Before and after totality, be sure to record your viewing site and the people who you shared this great event with.
Attend an event
Trust me when I say you’ll enjoy the eclipse more if you hook up with like-minded people. The Bonne Terre Airport is hosting a 3 day event. 2 days of Festival AND the Solar Eclipse on the 21st. Mineral Area College is also hosting an Eclipse Viewing on their campus as well.
Credit: European Space Agency Astronaut Sam Cristoforetti (@AstroSamantha)