Solar Eclipse - August 21, 2017

1999 European Solar Eclipse
This is a picture of the 1999 Solar Eclipse in Europe during Totality.

On August 21, 2017 the Sun will disappear behind the Moon causing a Solar Eclipse that will stretch across the United States from Oregon to South Carolina. This will be a path 70 miles wide path of total Solar Eclipse. The eclipse will not only darken the sky, but will cause a rapid temperature drop and the Corona of the Sun will be visible. Depending on where you are located the period of "Totality" could last up to 2 minutes and 40 seconds.

A total Solar Eclipse happens when the Moon appears to completely cover the Sun. Because the Moon is about 239,000 miles from Earth, the Moon appears to be the same size of the Sun and covers it. It is actually simple math, or Geometry that works in our favor. But this will not always be true. The Moon moves away from the Earth at a rate of 3.8 cm (1.49606 inches) per year. Eventually the Moon will look smaller in the sky and it will not completely cover the Sun and we will no longer have totality during Solar Eclipse. But we do not have to worry about this in our lifetime, it will take billions of years for this happen. Initially the moon was a mere 14,000 miles from earth and it has taken 4.5 billion years for it to get out to its present orbit. The Earth and the Moon both exert a gravitational force on each other and this is what causes tides on earth. The tidal bulge puts a small amount of energy into the Moon, and this pushes the Moon into a higher orbit. Just like a merry-go-round on a children's playground, the faster you go, there is more force pushing you outwards. But this outward energy causes the Moon to slow down. Eventually the Moon will be far enough out that it will cause the Earth's rotation to slow down. 4.5 billion years ago days on Earth were 5 hours long and today they are roughly 24 hours long. So in 4.5 billion years a day will last 43 hours on Earth. This slowing down will cause the Earth to wobble and will have an effect on our seasons and big swings in temperature. Nothing on Earth would survive this, but again, this is 4.5 billion years from now.

Eclipse Path with Percent
This picture shows the path and percent of Totality during the August 21, 2017 Solar Eclipse.

Even thought the "Path of Totality" is only a 70 mile wide swath as it passes over America, even people in south Texas will have a 60 percent eclipse, as will people in northern Maine. Here is southeast Mississippi the eclipse will be at 85 percent, as will central Oklahoma. I am planning on being at my sister's house in Lebanon, TN and it is in the path of totality. So there is not a real bad place in the United States to view the eclipse. This may be the last chance I get to see a total Solar Eclipse unless I travel overseas. has an excellent website discussing the difference between magnitude and obscuration. Obscuration is defined as the percentage or fraction of the sunís area being covered by the moon at a given point in time. Magnitude is the fraction of the sunís diameter being covered by the moon. The umbra is the first of two shadows that are cast by the Moon and it gets smaller as it reaches Earth. The other shadow is called the penumbra and its shadow gets larger as it reaches Earth. If you are in the umbra you get a total eclipse and if you are in the penumbra you get a partial eclipse. If you can get to a site with 100 percent totality, do it!

Eclipse Times
This picture shows the time that the Partial Solar Eclipse begins across the U.S.

The partial eclipse will start at 1:17 p.m. EDT on the South Carolina coast at an altitude of 69°-46° and leaves the Oregon coast at 9:05 a.m. PDT with an altitude of 28°-51°. Note that these are the starting times of the partial eclipse, not the peak times. The longest period of the eclipse will be over the eastern part of the U.S. with 2 minutes and 40 seconds of totality.

Path over Tennessee
This picture shows the path of the eclipse as it travels over the state of Tennessee.

One of my sisters and her husband live on the south side of Lebanon, TN, in the path of totality and very near the center of that path. They live on a very large hill with a full, unobstructed view of the sky. This will be a great location to observe the eclipse. I will be at the Huntsville, Alabama Hamfest on Saturday and Sunday morning and then I will drive another 2 1/2 hours north to my sister's house and get the telescopes setup for the eclipse on Monday. I already have all the telescopes, filters, solar glasses, and cameras ready for the event. We will be solar safe with our eyesight!

If you have not made your plans for the eclipse, you still have time to plan for this once in a lifetime event!