Monday afternoon, right here in Maryland, weather permitting, you can see the Great Solar Eclipse of 2017, though it won’t be completely total here. In Maryland, it will be about 83% but still it should be a fantastic sight. The eclipse runs from about 1:18 pm until 4:00 pm. The peak of the eclipse will be at about 2:43 pm. Remember not to look directly at the sun unless you have purchased special sun-viewing glasses, ordinary sunglasses aren’t enough to prevent eye damage. After 4:00 pm, the eclipse will be over. Don’t miss it!
The first total solar eclipse to cross the continental United States in 99 years will occur (August 21st, Monday). Though only about 5% of the surface area of the United States falls along the path of totality (the line of the Moon’s shadow), millions of us will gather along that path to witness one of God’s greatest wonders. My wife and I and two college friends have planned to meet in Tennessee along that path to see it, and each other.
What happens for a solar eclipse, is that the Moon passes directly in front of our Sun and blocks all of its light for a period of from one to seven minutes. The August 21st eclipse will have a totality period of 2 minutes and 41 seconds maximum. The reason for the short length of totalities is the fact that the Moon is small and casts a small shadow (only about 165 miles in diameter). The reason we do not have eclipses every month is that the Moon orbits us in a path that varies by about 5 degrees to the Earth/Sun line (our orbit around the Sun). The geometries of all these motions establish “eclipse seasons” which are six months apart, and which drift 11 days earlier each year. Another pattern involving eclipses is the Saros, which even ancient Greeks and Babylonians noted. Exact eclipse conditions repeat after 18 years and 11 days. One particularly long eclipse of nearly seven minutes in Baja California on July 11, 1991, was followed by another 6 1/2 minute totality eclipse on July 22, 2009.
There will be no eclipses at all in 2018, one in Chile and Argentina in 2019 and again in 2020. In 2021 Antarctica will see one; 2022 has none at all, and in 2023 an eclipse of only one-minute totality hits a remote region of Mexico. But on April 8, 2024, an eclipse of 4 minutes totality will pass over several large cities in the USA, starting in Texas and going northeast over Cleveland, Buffalo, Syracuse, New York, and Burlington, Vermont.
For those of us who stay in Maryland, the eclipse will still be seen, but no amount of totality will be visible. It will start here at home at 1:18 pm and reach maximum coverage at 2:42 pm. 83% of the Sun will be blocked, with the Sun looking like a crescent across the top of the Sun’s disk. The eclipse ends, when the Moon passes completely away from the Sun at 4:01 pm.
Let me remind everyone that looking at the eclipse, THAT EYE PROTECTION IS NECESSARY TO AVOID DAMAGE TO THE EYES. Sunglasses are not enough. Approved filters and special sun-viewing glasses are required. These can be ordered online. With 83% of the Sun blocked, also take a look around you and notice the reduced light on the ground and look for odd shadows of crescents on the ground as sunlight filters through tree leaves. But look often during the afternoon over the 2 3/4 hours of the passing of the the Moon over the Sun. Watch it advance and retreat over that period of time. But again, the eclipse in Maryland will not be fully total. You must look with approved eye protection. Not just sun glasses.
Sky-watchers should also remember that August gives us 31 nights of worthy celestial sights in addition to the eclipse. Jupiter dazzles in the southwest sky after dark and does not set until 11 pm. Saturn also rides up in the southern sky some 30 degrees above the horizon and offers wonderful views for those who have telescopes to use. The summer Milky Way, when our line of sight in the evening is toward the galaxy center gleams as our eyes scan from the southern horizon up and over toward the northeast, passing from Sagittarius, through Cygnus, and on toward Cassiopeia. This is especially delightful to see when using binoculars. Venus is 20 degrees up in the eastern sky before dawn and unmistakable at –4.0 magnitude. On August 19, it sits just above a very thin crescent Moon. And the Perseid meteor shower, always one of the year’s best peaks on the early morning of August 11 and 12. Even though the bright waning gibbous Moon will be in the sky then, the Perseids are bright meteors, and we should still be able to see some. Look northeast anytime from midnight to dawn.