Aug 15 2017

The Great American Eclipse

By Susan Hill Smith for The Island Eye News

“It’s really an emotional experience that you experience not just with your eyes, but your whole body.”
Professor Terry Richardson

Expect a lot of jostling for position as people consider viewing spots for the Aug. 21 “Great American Eclipse,” and don’t be surprised if the event draws some extra celestial attention to Isle of Palms, the final U.S. city the moon’s shadow will touch before heading into the waves of the Atlantic.

Sky Map: The total eclipse will give us a quick chance to stargaze. This map by College of Charleston Professor Terry Richardson indicates the position of stars and planets that should be visible to South Carolina viewers in the darkness when looking southwest from the centerline of the eclipse. It shows stars brighter than magnitude 1.6 unless they are so close to the horizon they can’t be seen. The size roughly indicates the star’s brightness. Regulus is just over one degree from the eclipsed sun and the sun’s corona may wash it out.

The last time the Southeastern coast of the United States had such prime viewing for a total solar eclipse was in 1970, making this a first-time event for many, and one to remember for the ages.

“Wild Dunes gets the last view of the moon taking a bite out of the sun before the moon’s shadow moves offshore.”
Professor Terry Richardson

Weather permitting, a partial eclipse will be visible to the entire North American continent that Monday. However, the “path of totality,” within which people will have a rare chance to experience the complete absence of sunlight during daytime hours, will be up to 168 miles wide and affect portions of 12 states.

Eclipse Terms Explained
Baily’s beads: The effect seen just before and just after totality when only a few points of sunlight are visible through valleys around the edge of the moon.
Chromosphere: The lower atmosphere of the sun just above the photosphere that appears as a thin crimson ring around the edge of the sun during a total solar eclipse.
Corona: The upper atmosphere of the sun. It appears as a halo around the sun during a total solar eclipse.
Diamond ring: The effect seen in the few seconds just before and after totality of a total solar eclipse when there is a single point of sunlight brilliantly shining through a valley on the limb of the moon.

The umbra — the moon’s complete shadow — will speed across the country, starting in Oregon and ending in South Carolina, where it will run diagonally from the Upstate’s northwest corner to our eastern shores, impacting 13 counties, including most of Charleston County.

Path of totality: The 168-mile wide path that the moon’s shadow traces on Earth during a total solar eclipse.
Photosphere: The bright, visible surface of the sun.
Penumbra: The part of a shadow – as of the moon or Earth – within which the source of light, such as the sun, is only partially blocked.

Even within the path of totality, the length of time viewers can experience the eclipse will vary based on location. In general, the closer you are to the center of the path, the longer you will be in darkness, with the maximum amount of possible total eclipse time in any spot being about 2 minutes and 41 seconds, according to NASA.

Shadow bands: Faint ripples of light sometimes seen on flat, light-colored surfaces just before and just after totality.
Totality: During a solar eclipse, this is the period when the sun’s photosphere is completely covered by the moon.
Umbra: A complete shadow – such as that of the moon or Earth – within which the source of light, such as the sun, is totally hidden from view.
Source: NASA

On our islands, the partial eclipse will start just after 1:17 p.m. and end at around 4:10 p.m. The total eclipse begins at 2:46 p.m. and ends at 2:48 p.m. Looking directly at the sun and moon could cause eye damage, so be sure to wear eclipse glasses with a filter that meets the ISO 12312- 2 standard.

Terry Richardson, a College of Charleston professor of physics and astronomy, made some calculations that showed the local range and impact. Richardson determined that the total eclipse will last 1 minute, 30.6 seconds at White Point Garden on peninsular Charleston; 1 minute, 50.5 seconds at Breach Inlet; 2 minutes, 8.2 seconds at Isle of Palms’ northeastern tip; and 2 minutes, 12.4 seconds on Dewees Island’s front beach.

To get the maximum amount of total eclipse time in the Lowcountry, you would need to go farther north along the coast, closer to the village of McClellanville — where it will last 2 minutes, 32.9 seconds, according to Richardson’s calculations. McClellanville is also the last town or city touched by the total eclipse, with the centrality of the moon’s shadow completing its path across the country just eight seconds short of 2:49 p.m.

However, the Isle of Palms will be the last U.S. Municipality in the partial shadow of the moon if you consider the time the shadow leaves the northeastern tip of the island, at 4:10 p.m and 14 seconds. “Wild Dunes gets the last view of the moon taking a bite out of the sun before the moon’s shadow moves offshore,” Richardson says.

For those in the path of totality, it promises to be a sensory treat, with something akin to a 360-degree sunset, a noticeable temperature drop and a possible quieting of animals tricked into thinking it’s night. “It’s really an emotional experience that you experience not just with your eyes, but your whole body,” he says.

With all the traffic concerns, the professor encourages folks with an easy beachfront view on Isle of Palms to take advantage of their unique position. After all, South Carolina won’t be treated to another total eclipse until 2052.

This article originally appeared in the Summer 2017 edition of SiP magazine.

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