12. 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.

13. 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.

14. The end of the eclipse for the U.S. is not on land. The center line’s last contact with the U.S. occurs at the Atlantic Ocean’s edge just southeast of Key Bay, South Carolina. I’m pretty sure the crowd won’t be huge there.

15. 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.

16. This eclipse will be the most-viewed ever. I base this proclamation on four factors: 1) the attention it will get from the media; 2) the superb coverage of the highway system in our country; 3) the typical weather on that date; and 4) the vast number of people who will have access to it from nearby large cities.

17. Only one large city has a great view. Congratulations if you’re one of the 609,000 people lucky enough to live in Nashville. The city center and parts north of it will experience 2+ minutes of totality. Unfortunately, that’s the only large city with a great view. In the tally below, column 1 lists 25 other large metropolitan areas. The second column shows the amount of the Sun’s surface the Moon will cover as seen by viewers in each city.

Atlanta 97 percent Boston 63 percent Chicago 87 percent Cincinnati 91 percent Dallas 76 percent Denver 92 percent Detroit 79 percent Houston 67 percent Indianapolis 91 percent Las Vegas 72 percent Los Angeles 62 percent Memphis 93 percent Miami 78 percent Milwaukee 83 percent Minneapolis 83 percent New Orleans 75 percent New York City 72 percent Oklahoma City 84 percent Philadelphia 75 percent Phoenix 63 percent Pittsburgh 81 percent Portland 99 percent Salt Lake City 91 percent Seattle 92 percent Washington, D.C. 81 percent

Now a brief follow-up: about half of both Kansas City (pop. = 464,000) and Saint Louis (pop. = 318,000) lie within the path of totality. Unfortunately, the center line doesn’t pass through either of them. An educated guess then, tells me that most residents interested in the eclipse will drive 30 minutes or so for an extra two minutes of totality.

18. A few small cities are well-placed. Here’s a list of smaller municipalities either on the center line or near it with their approximate populations.

Carbondale, Illinois 26,000 Casper, Wyoming 58,000 Columbia, Missouri 113,000 Columbia, South Carolina 132,000 Grand Island, Nebraska 50,000 Greenville, South Carolina 61,000 Hopkinsville, Kentucky 33,000 Idaho Falls, Idaho 58,000 Jefferson City, Missouri 43,000 Paducah, Kentucky 25,000 Saint Joseph, Missouri 77,000 Salem, Oregon 157,000

19. 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.

20. 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.

21. 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.

22. 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.

23. Maximum totality is not the longest possible in 2017. The longest possible duration of the total phase of a solar eclipse is 7 minutes and 32 seconds. Unfortunately, the next solar eclipse whose totality approaches 7 minutes won’t occur until June 13, 2132. Its 6 minutes and 55 seconds of totality will be the longest since the 7 minutes and 4 seconds of totality June 30, 1973.

24. The future is bright but long. The next total solar eclipse over the continental U.S. occurs April 8, 2024. It’s a good one, too. Depending on where you are (on the center line), the duration of totality lasts at least 3 minutes and 22 seconds on the east coast of Maine and stretches to 4 minutes and 27 seconds in southwestern Texas. After that eclipse, it’s a 20-year wait until August 23, 2044 (and, similar to the 1979 event, that one is visible only in Montana and North Dakota). Total solar eclipses follow in 2045 and 2078.

25. This event will happen! As astronomers (professional or amateur), some of the problems we have are due to the uncertainty and limited visibility of some celestial events. Comets may appear bright if their compositions are just so. Meteor showers might reach storm levels if we pass through a thick part of the stream. (Oh, and the best views are after midnight.) A supernova as bright as a whole galaxy is visible now, but you need a telescope to view it. In contrast, this solar eclipse will occur when we say, where we say, for how long we say, and in the daytime, no less. Guaranteed!