As an astronomy instructor, I spoke with students about the “solar eclipse in 2017.” Well, it’s upon us.

On August 21, the moon’s shadow races across the United States from the northwest to the southeast, with its path crossing through southern Illinois.  As the moon revolves to the east and passes directly in front the sun, the shadow’s width varies from about 37 miles to 71 miles.  Within this “path of totality,” the moon completely blocks out the sun.  In southern Illinois, the total eclipse reaches 2 minutes, 40 seconds.  Although the entire eclipse process takes nearly three hours.

The images above are from the annular (ring) eclipse from 2012.  During that eclipse, the moon appeared to be too small to cover the sun, as our lunar neighbor was too far away to completely cover the sun.

NASA Photo

For those travelling to locations in the darkest part of the eclipse’s path, they will see a total eclipse with the moon covering the sun, revealing the sun’s corona, commonly known as the sun’s “atmosphere.”  For the scant few minutes, of “totality,” the corona is visible because normally, the glowing face of the sun overwhelms this thin, hot crown of gas.

Viewing the Eclipse From Chicago

Viewing the eclipse is always a challenge and potentially can damage eyesight.  The gleaming orb of solar intensity is difficult to look at anytime.  Its intensity normally causes us to look away.  To ensure safe viewing, use indirect methods, such as merely sitting under a tree.  The overlapping branches, naturally produce tiny pinholes.  Under a tree on any typical day, you’ll see patterns of shade and spots of light.  These spots are images of the sun projected on the ground.  During an eclipse, images of the eclipsed sun appear on the ground.

In this image notice the dozens of eclipse images that are displayed on the wood deck.  On a windy day the images dance on the ground as the leaves respond to the changing air patterns.

Even in large group settings, such as schools, these indirect methods give everyone a continuous view of the slowly moving moon across the sun’s face.

In this view a student has made a hole in a paper plate.  When held in sunshine, the plate casts a shadow and a tiny hole in the plate allows the eclipse to project through into the shadow made by the plate.

The famous solar projector made with a box that has aluminum foil that is place over a hole in the box.  Multiple holes in the foil show a solar display.

Any object with multiple holes such as a straw hat (above) or colander will project a pattern of eclipses.

The solar image can be projected through a telescope or binoculars.  Never look through the optical device, even with filters.

In this image the telescope has a white card for projecting the solar image.

Here a projection through binoculars shows two images of the eclipse.

For schools that are in session on eclipse day, show students how to view the eclipse safely.  It would be an ideal time for students to build eclipse viewers, solar cookers and other solar projects so they can be outside to try out their work.

Chicago’s View

The total eclipse is not visible from Chicago.  The maximum eclipse (amount of the sun covered by the moon) is 87%.  The eclipse begins in Chicago at 11:54 a.m. CDT with the sun high in the southern sky.

At this time, the edge of the moon appears to be touching the edge of the sun.

The moon gradually moves in front of the sun as shown in the chart above for 30 minutes from 12:30 p.m. to 1 p.m.

The best part of the eclipse occurs during the next 30 minutes as the moon reaches its maximum eclipse (87%) at 1:19 p.m.

During the next 72 minutes the moon begins to uncover the sun, with the moon exiting from the sun’s face at 2:42 p.m.

Robert C. Victor’s Eclipse Resources

Robert C. Victor, former staff astronomer at Abrams Planetarium, has provided the following list of resources for those who want further details about the August 21, 2017, eclipse.

Solar Eclipse information and Resources

• www.eclipsewise.com/solar/SEnews/TSE2017/TSE2017.html
• https://eclipse.aas.org/
• https://eclipse2017.nasa.gov/
• http://www.skyandtelescope.com/total-solar-eclipse-august-2017/
• https://www.astrosociety.org/education/2017-solar-eclipse-information-resources/
• https://static.nsta.org/extras/solarscience/SolarScienceInsert.pdf
• http://eclipsophile.com/total-solar-eclipses/total-solar-eclipse-2017-august-21/
• http://aa.usno.navy.mil/data/docs/Eclipse2017.php
• http://www.astronomy.com/great-american-eclipse-2017
• https://www.greatamericaneclipse.com/

Future American Total Solar Eclipse

The next total solar eclipse visible in North America is on April 8, 2024.  The moon’s shadow sweeps from the Pacific Ocean through Mexico and into Texas moving rapidly northeast.  It crosses through Southern Illinois into Indiana and Ohio.  Then it moves into New York state and then into the New England states.  It crosses into Canada and into the Atlantic Ocean.  From Chicago 94% of the sun is covered.