Path of Totality for August 21, 2017 Eclipse
A special event is coming up August 21, the scope of which hasn’t occurred for 99 years! If you had grandparents at that time in Portland, Oregon; Denver, Colorado; Oklahoma City, Oklahoma; or Orlando, Florida, to name a few, they would have most likely seen it, or at least heard about it.
As you’ve probably figured out, I’m talking about the Great American Eclipse, so called because it crosses the entire USA from Oregon to South Carolina, and is only visible in the Continental USA. Last time we had one that stretched from “sea to shining sea” was June 8, 1918. That one started in Washington State and struck a diagonal path across the US, clear down to Florida and slightly beyond. When I gave this talk at my Toastmasters meeting recently, one of the members recalled her mother, who lived in Oklahoma, seeing it, and being amused when the chickens were confused and went to roost when it got dark.
Eclipse 101
Total solar eclipses are relatively rare. First of all, they only occur with a New Moon. Why? Because that’s when the Moon is between Earth and the Sun, allowing its shadow under the right conditions to reach the ground. But we have a New Moon every month! Why don’t we have a solar eclipse every month?
Easy–it’s a matter of alignment. Remember, both the Sun and Moon are moving! More correctly, the Earth is rotating, making the Sun appear to move across the sky in a path called the ecliptic, which changes as far as its elevation above the horizon is concerned, based on the seasons, which are caused by the Earth’s axial tilt. The ecliptic is highest for the summer solstice. This maximizes the Sun’s path and explains why the days are longer. The opposite is true in winter. So, the Sun is not only “moving” across the sky, but changing it’s elevation above the horizon. I knew someone once who loved to describe unpredictable people by saying that for them “The Sun always comes up in a different place.” Ironically, this is true. If you’ve never noticed, it’s never too late to start.
The Moon orbits the Earth, but where its orbit crosses the ecliptic is not static, but moves a few degrees each month. Thus, the Moon’s location is also constantly changing, though it does so in a predictable manner. For an eclipse to happen, both the Sun and Moon need to be in the location where their paths cross, placing the Moon exactly between Earth and the Sun, casting its shadow on the ground directly below. You can see how predicting when and where eclipses will occur is not a simple matter. Nonetheless, the antikythera device was able to predict eclipses and so were the Mayans, because as their precise calendar indicates, they understood solar and lunar cycles.
You may be surprised to find out that there are two solar eclipses every year, but they’ll be visible in different locations. With two-thirds of the Earth’s surface oceans, many occur there and go unnoticed, save for physicists dedicated to solar research, especially those trying to determine why the Sun’s corona is several millions of degrees, while its surface, known as the photosphere, is a mere 10,000 degrees Fahrenheit. A total eclipse is the only time when the magnificent corona is visible. Researchers suspect the corona’s temperature is related to the Sun’s magnetic field, but they’re still trying to figure out why.
Types of Eclipses
Not all eclipses are total. There are also partial and annular. Partial is when the Sun and Moon don’t line up exactly, so only a portion of the Sun is obscured. In this case, a total eclipse is not seen anywhere. However, note that a partial eclipse is also what those located outside the narrow band of totality will see on August 21, again because the alignment is not perfect.
Annular Eclipse
An annular eclipse occurs when the Moon is farther away from the Earth and therefore smaller, such that it doesn’t entirely cover the Sun. Then, instead of the magnificent corona visible during a Total Eclipse, you see a ring. In some of these less than ideal cases, the Moon’s shadow doesn’t even reach the Earth.
Eclipse Path of Totality
To see the upcoming event as a total eclipse, you’ll have to be somewhere along the red stripe shown on the map. The location where totality will be longest (2 minutes 41.6 seconds) is in the vicinity of Carbondale, Illinois. Oddly enough, another total eclipse in 2024 also crosses that location. It’s very unusual for this to happen; often centuries pass before a total eclipse is visible again from the same place.
Paths of 2017 and 2024 Eclipses. “X marks the spot” over Carbondale, Illinois.
Unfortunately, the eclipse will not be total where I live, here in Texas. Rather, it will be a partial eclipse that covers 65-70% of the Sun. It will start here around 11:35 am, be at its maximum around 1:10 pm, and end around 2:40 pm. However, space cadet that I am, I’ll be traveling somewhere that it’s total.
Safe Viewing Tips
To safely view the eclipse, you need to protect your eyes with special glasses or some other sort of filter. Ordinarily sunglasses are insufficient, so don’t even think about using them alone if you value your eyes. A pinhole camera will show it, too, or look at the shadows of leaves beneath a tree to see thousands of tiny Sun crescents.
You can get special ISO Certified glasses, but hurry since they’re selling out fast. Sources are listed below. Note that glasses suitable for you to watch the eclipse are NOT sufficient if you’re using a camera or telescope! In that case you need a solar filter for the lens! Solar filters are available for most regular cameras. If you value your cell phone, don’t plan on taking pictures of the eclipse with it because it’ll burn it up. Remember starting a fire with a magnifying glass when you were a kid? Same idea. Another option to special eclipse glasses is #14 welder’s glass, which could also work to protect your cell phone.
The only time it’s safe to look at a solar eclipse without eye protection (for you or your camera) is during totality, i.e. when the Sun is entirely covered by the Moon. That is preceded by a final glint from the Sun they call the “Diamond Ring”, which also occurs as the eclipse ends, but that flare could be enough to zap your camera or cell phone, so bear that in mind. Totality doesn’t last long, usually between 1 – 2 minutes. Nonetheless, you should enjoy it with your natural eyes while it lasts to enjoy it’s full impact and beauty.
Many people go throughout their lives without ever witnessing a total eclipse. I’ve seen partials, but never a total, so I’m flying to Utah to visit my daughter and her family, then we’ll drive into Idaho to the band of totality. I’m sure it will be a get-together we’ll never forget. It’ll be worth watching, even from here in Texas. If nothing else, you can see firsthand why the ancients were frightened when it appeared something was consuming their life-giving Sun.
Another Eclipse is coming!
If you live somewhere outside the band of totality and can’t travel to see the total eclipse this time, then you can look forward to the one in 2024, when there will be another one. (You can see the path as the second band that forms the “X” in the map above.) For me, here in Central Texas, it will be right on our doorstep! In fact, the center of the path of totality goes right over Lake Buchanan, northwest of Austin, meaning I’ll be able to watch it from my front yard! Come April 2024, there will be a lot of people around here praying for clear weather.
RESOURCES
Eclipse Information
www.greatamericaneclipse.com
www.earthsky.org
http://eclipse.gsfc.nasa.gov/eclipse.html
http://www.valkyrieastrology.com/Makeover/Planets/Eclipses.htm (my astrology website)
Eye Protection
www.rainbowsymphonystore.com (bulk orders)
https://www.teachersource.com/product/1892/nyeglasses
https://www.space.com/36941-solar-eclipse-eye-protection-guide.html
https://www.eclipseglasses.com/products/
https://weldingsupply.com/
Photo Tips
http://www.eclipse2017.org/2017/photographing.HTM
http://www.whas11.com/news/experts-warn-not-to-use-cell-phone-camera-for-2017-solar-eclipse/457560482
Marcha's Two-Cents Worth 