The Great American Eclipse This August

Read tips and more from astronomer Matt Benjamin, who spent the last decade managing Fiske Planetarium at the University of Colorado Boulder. Matt was an invited speaker and teacher for NASA’s Journey Through the Universe program. He has also been visiting Ketchum for 35 years with his family and considers Central Idaho a home away from home.

Get ready for an experience of a lifetime! The Great American Eclipse on Monday, August 21, will be the first contiguous eclipse throughout the United States since 1979. Over 100 million people are within a day’s drive of the path of totality. The 70-mile-wide path from Payette to Driggs is primed for one of the best views of this display from Mother Nature. Don’t settle for 99% of an eclipse—make sure you get yourself within the path of totality.

What Is a Solar Eclipse?

A total solar eclipse is the more dramatic of the two types of eclipse that we see from Earth. A solar eclipse is when the moon moves in front of the sun. A lunar eclipse is when the earth casts its shadow on the moon. These two eclipses happen at opposite phases of the moon. The solar eclipse always occurs at a new moon and a lunar eclipse always occurs at a full moon.

https://www.nasa.gov/sites/default/files/styles/1920x1080_autoletterbox/public/solar-eclipse-diagram.jpg?itok=nhgmGAbX
*NASA diagram

The Path of Totality in Idaho

http://tropicalsails.com/wp-content/uploads/2015/11/ID_web.jpg

Idaho offers some of the most pristine wilderness and landscapes where you can view this cosmic alignment. The closer you are to the centerline running from Weiser east through Stanley and Driggs, the longer the totality lasts. So if you are on the outer edge of totality, you may experience only a few seconds of full eclipse.

Hotels and campgrounds have been booked for months and even years. But backcountry enthusiasts can make a 2- to 3-day trip into some of this magnificent wilderness. When choosing your spot, find a place with a clear view to the south. For those doing a day trip, leave very early Monday morning. Tens of thousands of people are coming to Central Idaho for the eclipse. The Sawtooth Valley anticipates around 30,000 people. Driggs and Rexburg may see just under 100,000, and Jackson Hole on the other side of the Tetons expects 120,000 people.

Give yourself plenty of time to get where you plan to view the eclipse, and keep in mind that the trip home will be the same story. With school in session, many people will travel home Monday afternoon and evening. If possible, extend your stay through Tuesday.

A Play by Play of the Total Solar Eclipse

First things first, on the morning of August 21, you should find a comfortable, safe place to watch from. From beginning to end, this eclipse will last a little under 3 hours. You don’t want to be walking around while trying to view the eclipse.

During this whole time, you must wear certified eclipse glasses or make a pin-hole camera to see a projection of the sun and moon. Looking at the sun for even a short time can be extremely damaging to your eyes. During the roughly 2 minutes of totality, you can take your glasses off and safely view the eclipse with your naked eye.

  • 10:15 am (eclipse starts)—You can expect to see the moon take the first “bite” out of the sun. For the next hour, things proceed slowly as the moon continues to eclipse the sun. Check the progress every 5 to 10 minutes.
  • 11:20 am—The climax of the eclipse begins. Leading up to this, you will notice the sky dim a bit. One of the most remarkable parts of a total eclipse is watching the shadow of the moon move across the ground. If you can see a few miles to the west, look for this dark line moving toward you. The speed of this shadow is about 2,000 mph or about half a mile per second.
  • 11:29 am (totality)—Once the darkness is upon you, it is safe to remove your eclipse glasses and watch with your naked eye. During totality, pay attention to your surroundings. Animals may act strangely during totality as they get confused about the time of day. Depending on the sun’s physical activity, you may see streamers and rays emanating from the disk. These rays and streamers are a window into the outer parts of the sun’s atmosphere called the corona. This superheated region of the sun is dominated by plasma that blasts through our solar system. This is known as the solar wind. The corona is still a mysterious part of the sun  since little is understood about how these charged particles accelerate to form the solar wind. Totality will last for approximately  2 minutes and 15 seconds. I’m willing to bet that this will be one of the most incredible moments of your life!
  • 11:31 am—Put your eclipse glasses back on and be on the lookout for the first rays of sunshine to come back into view. This first light is known as the “diamond ring” for the apparent glimmer along the disk of the moon. Throughout the rest of the eclipse, everything happens in reverse—the moon will slide farther off the sun until about 1:00 pm when the eclipse is over.
  • 1:00 pm—Time to celebrate!

Eclipse Viewing Tips

  • Plan ahead for food, water and supplies. Stores may be in short supply in and around the path of totality.
  • Wear sunscreen; you’ll be out in the sun at altitude for many hours.
  • Use certified (not knock-off) eclipse glasses for the entire eclipse except those two and a half minutes of totality. You can view totality without your glasses. (Sorry, ICL eclipse glasses are sold out.)
  • Bring a sweater. Temperatures can drop 10 to 20 degrees while the moon blocks the sun.
  • Bring a chair or blanket for comfort. The eclipse lasts almost 3 hours.
  • Avoid looking up while walking or hiking. Stop and enjoy, then move on to avoid falling and hurting yourself!
  • Look to the west just before totality to see the shadow of the moon move across the ground.
  • Put your camera away. Eclipses are among the hardest phenomenon to photograph.
  • Just watch! Totality will be the shortest two and a half minutes of your life so be present in that moment.
  • Pay attention to your natural surroundings. Animals are known to behave strangely when the darkness arrives. Many are tricked into thinking its sunrise or sunset.

Q&A About Eclipses

Most of us have seen one if not multiple lunar eclipses, while very few us have seen solar eclipses. Why is that? 

It is not because lunar eclipses occur more frequently. In fact, both types occur equally. The difference is that, during a lunar eclipse, anyone in view of the full moon can see the moon darken as it moves into Earth’s shadow. That usually corresponds to most of one hemisphere of the earth seeing a lunar eclipse. But during a total solar eclipse, just a swath 70 miles wide gets to see a complete blockage of the sun (totality). Because of how narrow this swath is, fewer people see it. Additionally, roughly 70% of the Earth is covered by water, so many of the total solar eclipses never cross over land (lucky for whales and dolphins, I suppose).

Why don’t we have eclipses every month? 

From our perspective, the sun and moon appear to move more or less on the same path in the sky, but their trajectory on the sky is offset by only about 5 degrees. This tiny difference is enough to prevent the sun and moon from lining up every month. Earth experiences two to five partial lunar and solar eclipses every year while the perfect alignment needed for a total solar eclipse only happens every 18 months or so.

https://www.nasa.gov/sites/default/files/styles/full_width_feature/public/images/230933main_ISSumbra_HI_full.jpg?itok=uOYsLPgg
*Image of moon’s shadow as seen from International Space Station, NASA

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