May Sky Talk | Total Eclipse Of The Sun! – Part I

MARK YOUR CALENDAR! On August 21st, nature’s grandest spectacle will happen and be visible to millions of people along a narrow path across the entire continental United States.  This is an (almost!) once-in-a-lifetime event not to be missed at all costs.  And as you read on, you will clearly see why!

A total eclipse of the Moon occurs where the Earth’s huge shadow cone engulfs the lunar surface, typically for an hour or more and is widely visible.  A total eclipse of the Sun, on the other hand, is caused by the Moon’s tiny shadow cone blocking out the Sun for only a few brief minutes as seen from a narrow path swept out by its shadow.  But there is simply no comparison of the visual impact of the two events!

As the Moon slowly encroaches upon the Sun, the lighting around you begins looking a bit eerie and when it has covered most of the solar disk a kind of twilight sets in.  Suddenly—at the moment of totality—as if someone turned off a light switch, it goes dark!  The stars and planets appear.  The wind kicks up.  Birds head for their nests.  And the temperature rapidly drops 20 degrees or more.  The Sun’s beautiful pearly corona (its outer atmosphere) becomes visible, and crimson prominences appear around the edge of the solar disk.  Within two minutes—more or less depending on where you are—totality ends and daylight returns.   No wonder so many call this an unforgettable spiritual event.

Averaging 68 miles wide, the Moon’s dark shadow first touches down mid-morning on the West Coast in Portland about 10:15 a.m. PDT and then crosses 12 states, ending in the afternoon off the East Coast in South Carolina before lifting off and out over the Atlantic Ocean about 2:45 p.m. EDT.  Those within this narrow path will see totality.  All others will see only a partial eclipse, the degree depending on how far from the path they live.  Wherever you are, it’s well worth traveling so you are located somewhere within the path of totality.  Although this event is still several months off, we’re covering it early to give you time to find a suitable viewing site, and accommodations if needed (hotels are already filling up fast!)—and perhaps organize an informal “eclipse party” with friends, relatives and/or neighbors.  Among the multitude of sites on the Internet giving times for specific locations across the country, one of the best that provides detailed information on a state-by-state basis can be found at:

One caveat you must be aware of: the weather!  People have traveled all across the country—and even around the world—to see an eclipse, only to be clouded out at the last minute!  But the risk is well worth taking of putting yourself in the path of totality, whatever it takes.  (This is an advantage of eclipse cruises since a ship can be relocated to another area if one is forecasted to be clouded out.)  In the event of overcast skies where you are, NASA and several observatories will be live-streaming the eclipse.

The all-important (make that vitally important!) viewing precautions, and information on future eclipses will be covered in the June installment of Sky Talk.  In closing this month’s, I can’t help but point out an amazing “cosmic coincidence” that makes this spectacle possible: the Sun is 400 times larger than the Moon—but the Moon at its average distance happens to be 400 times closer, perfectly covering our Daytime Star!

— James Mullaney

Former assistant editor at Sky & Telescope magazine & author of nine books on stargazing.  His latest, Celebrating the Universe!, is available from