Spectacular sky show is on the way

Few sights in nature can equal the exquisite and awe-inspiring beauty of a total solar eclipse. To gaze upon the sun's pearly white corona, upon which orange colored prominences occasionally dart from the limb of the moon, all the while engulfed in darkness, is an experience never to be forgotten.

And, as luck would have it, the laws of celestial motion will align in such a way that this phenomenon will grace the skies of many Americans from Oregon to South Carolina on August 21, 2017.

Traveling at more than 2,400 miles per hour, the umbra (where a total eclipse is visible) of the moon's shadow will first contact the west coast of the United States just north of Newport, Oregon, at 10:15:50 a.m. PDT on Monday, August 21, then race eastward across the state, exiting it by 10:27:10 a.m. In this relatively short span of time, weather permitting, hundreds of thousands of Oregonians and visitors will have witnessed one of the finest events that astronomy has to offer.

But what should observers do to position themselves for a satisfactory peek at the eclipse? Is it worth the time and fighting possible heavy traffic to get somewhere close to the centerline of the total phase of the eclipse? The duration of totality in Madras, the Painted Hills, Mitchell, Unity and other locations close to this centerline will be two minutes or longer. The maximum duration occurs in Kentucky and will be about 2:40.

If you stay in Sisters you will have only 30 seconds of totality. At the northernmost locations that you can reach from Wilt Road or Green Ridge Road, you will have a duration of almost two minutes.

From Wilt Road this will involve some rough sections of road, but a closer location called "Squaw Flat" before the road gets really rough may be a good place to observe and will have a totality duration of about 1:30.

At Camp Perry South, reached from Green Ridge Road, the duration of totality will be 1:57. However, Lake Billy Chinook locations are more easily accessible from the east and will probably be very busy on eclipse day.

There is an interactive map here: https://eclipse2017.nasa.gov/sites/default/files/interactive_map/index.html . On this map, you can click on a location and find the time and duration at any location in the U.S.

In this area, the total phase of the eclipse will start at about 10:19 a.m. First contact, when the partial phase of the eclipse begins, is at about 9:06 a.m. Whether you are at a location comfortably before the eclipse begins or have barely made it into the path of totality, you should start by observing the partial phase of the eclipse using safe eclipse viewing filters.

There are many sources of such viewing devices. Sisters Astronomy Club will have a display set up at community events between now and the eclipse date and they will have viewers available for a small donation.

The Oregon Observatory in Sunriver has them for a modest donation as well. Any of these devices and other materials specifically labeled for visual observation of the sun can be used. Number 14 welding goggle filters are safe for such observation, too.

DO NOT use improvised "filters" such as exposed film or smoked glass.

As soon as you can no longer see any of the bright surface of the sun through your filters, you should start observing the total phase with your naked eyes or through a pair of binoculars or a low-power telescope. If you have filters for your binoculars or telescope, take them off as soon as you can no longer see anything through them when looking at the sun.

Why don't we get to see total solar eclipses more often?

The last total solar eclipse viewable from Oregon occurred in February, 1979, and the next one viewable within the United States will take place on April 8, 2024.

The plane defined by the earth's orbit around the sun is called the "ecliptic plane" because when the sun, earth and moon are aligned in this plane eclipses occur. The moon's orbit is inclined at 5 degrees to the ecliptic plane and therefore eclipses of the sun or moon do not occur every month.

If it were not so inclined, there would be a lunar and solar eclipse occurring every month: a lunar eclipse every full moon, a solar eclipse every new moon. If the moon's orbit didn't also go through some other regular variations, eclipse "seasons" would occur at the same time every year, with one or more partial or total eclipse occurring every six months when the moon's orbit carried it through the plane of the ecliptic.

Accurately accounting for the movements of celestial bodies that cause eclipses is so challenging that Isaac Newton once wrote to Edmond Halley that the theory of the motions of the moon made his head ache and kept him awake so often that he would think of it no more.

Sisters Astronomy Club has regular meetings on the third Tuesday of the month, July 18 and August 15 at 7 p.m.

in the Sisters Park & Recreation District Coffield Center.

The club holds public star observing programs, Stars over Sisters, at SPRD and the SHS parking lot on July 15, 9 p.m.

and August 19, 8:30 p.m.

Any of the events will be opportunities for the public to learn more about the stars and celestial events such as the eclipse.

The website www.sistersastronomyclub.org has many links to information about the upcoming eclipse and other sites for those interested in astronomy and the night sky.

Current astronomical news is regularly posted on the Facebook page www.facebook.com/ sistersastronomy.

You may email the authors with questions about the eclipse or any other questions about astronomy: [email protected]