Mark your calendar: August 21, 2017. Crowds from coast to coast will scramble into position. News crews will fall over themselves. Music videos will be filmed on location, memes will be born, and while some hearts will swell, others will undoubtedly be broken.

But you — reading this, now — you’ll be prepared when the eclipse rolls into town. On that future Monday, a total solar eclipse will rip straight across the United States, from Oregon, all the way to Charleston, South Carolina. For two minutes and change, the moon will completely blot out the sun, causing the sky to darken, stars to emerge, and the sun’s shimmery, iridescent coronal atmosphere to flare to life before your eyes. It’ll be a spectacular light show — and the first visible from the contiguous United States since 1979. Think the recent SuperBloodMoon lunar eclipse was cool? This will make your gyroscope wobble.

“Total solar eclipses are simply the most amazing natural sight that you can see,” says Michael Zeiler, a writer, illustrator and cartographer who’s logged seven eclipses and is the publisher, with his wife Polly, of the leading website for the 2017 event, greatamericaneclipse.com (a great additional resource is nationaleclipse.com). “The corona is the sun’s constantly changing atmosphere and is filled with streamers, loops, fans and explosive prominences. During totality, the entire sky is a dynamic light show with qualities of light you’ve never seen before.”

If you’re not convinced, just think of the buzz solar eclipses achieve when they occur elsewhere on the globe — amateur astro-geeks and hardcore eclipse-chasers travel to remote parts of the world to see them, locals snatch up protective eclipse shades like they’re candy, and each one makes news globally. I’ve seen two myself, one in Australia in 2012 and the other in the Faroe Islands this past March, and each experience was an adventure capped by a sublime, moving bit of celestial showmanship. So plan to take your friends and family. Or go solo. Or bring a date. Find a crowd, or enjoy it in solitude. There will be 2,500 miles of opportunity as the Moon’s circular shadow glides from sea to shining sea in just 90 minutes.

Eclipse Chasing 101

So You’re Gonna Give This Celestial Spectacle a Chance?

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Watchers’ greatest challenges will be choosing a spot with a low likelihood of cloud cover, and making sure you’re as close to the shadow’s centerline as possible. These are the critical variables. The width of the umbral shadow — that is, the moon’s circular shadow on the Earth’s surface, and the region that will experience the total eclipse (as opposed to the partial eclipse experienced by the rest of the continent) — ranges from only 35 to 71 miles wide during this eclipse. If you’re along the centerline of that shadow, you’ll have between 2 minutes and 2 minutes, 40 seconds of totality. (Totality refers to the complete blockage of the sun. For an hour or so before totality, the eclipse will be partial.) But every mile you stray from the centerline reduces that time significantly, such that viewers at the edge of the shadow’s path, only 15 to 35 miles away, will experience barely 10, 20 or 30 seconds of totality. So double-check your location rests on the centerline. That’s your starting point for planning your viewing.

There will be 2,500 miles of opportunity as the Moon’s circular shadow glides from sea to shining sea in just 90 minutes.

Next, you’ll want to gauge cloud cover along the path, initially based on historical data for the region you have your eye on, and then again in the days leading up to the event. Charts at Eclipser (published by Jay Anderson) will give you a good general overview. The best prospects are northern Oregon, Idaho, central Wyoming and western Nebraska.

Once you have your region chosen, start looking for hotels, booking flights, and reserving cars or RV’s soon, because they’re already going fast. Worst case, you can just drive to a good region and bring camping gear or find accommodations within a few hours’ drive. You’ll be able to make it an adventure by getting reasonably close and then heading to the shadow’s path on August 21.

What Causes a Total Eclipse?
Total eclipses occur because of a single, pretty unbelievable coincidence: the apparent size of the moon in the sky precisely equals that of the sun. The sun’s disk is exactly 400 times larger than the moon’s, but it’s also 400 times farther away. There’s variations of this rule, based on the elliptical orbits of the Earth and the moon, and that variation accounts for eclipses that aren’t total — sometimes the moon’s disk is smaller than the sun’s, and sometimes it’s larger. That’s why total eclipses are so rare.

On the big day, make sure you’re mobile, via your own vehicle or a rental. Weather conditions can change no matter where you are, so you may have to chase patches of clear sky in the days or hours before the eclipse begins, as I did in both Australia and the Faroe Islands. “Whether you stay in a hotel or camp, be ready to relocate to a nearby state if necessary,” Zeiler says. “Stock up with food, water, and keep a full tank of gas if you need to drive a couple hundred miles for a clear spot. Remember that there is plenty of room for everyone in the eclipse path, if you avoid the predictable areas where crowds may gather.”

How will this whole thing go down? Majestically, of course. The total phase of the eclipse begins at just after 10:00 a.m. for the West Coast and then it proceeds, with time changes, to just before 3:00 p.m. on the East Coast. Viewers wearing dedicated eclipse glasses will watch the moon slowly progress across the sun’s surface, gradually darkening it. Just before totality, the action will accelerate — stars will emerge, the sun’s corona will become visible, and phenomena such as the diamond-ring effect (the last bright flash of light before totality) and Bailey’s Beads (small glimmers of light seen through mountains and valleys on the moon) will be visible. When totality begins, you’ll be able to watch without eye protection as the bright halo of the sun surrounds the black center. When totality ends a few minutes later, the process just described proceeds in reverse order.

When the eclipse rolls in, be ready to photograph it, take selfies with it, or just sit back and enjoy the experience for what it is — a big old gift from the cosmos. And if you don’t, you’ll have a few years to wait. The United States won’t be able to enjoy another total eclipse until April 8, 2024. Oh and, yes, put that on your calendar, too.

Additional data about the 2017 eclipse and eclipses in general sourced from Eclipse Bulletin: Total Solar Eclipse 2017 August 21, by Fred Espenak and Jay Anderson.