Total Solar Eclipse or Partial Eclipse: Which Will You See?

What You Can (and Can't) See

Jeff DeTray from AstronomyBoy.com
Partial Eclipse

Partial eclipse from May 13, 2013 as viewed from Fremantle, Australia.  

Phillip Calais/NASA

total solar eclipse will sweep across the continent on August 21, 2017. However, most of us will see what is called a partial solar eclipse. A young Almanac fan shares a great video explaining the difference between a total eclipse and partial eclipse.

As you may have heard, you need to be located in the “path of totality” that crosses the country to see the total eclipse. See the map below. The path is just 150 miles wide—but the ribbon of darkness stretches from Oregon straight to the Carolina coast. If you don’t live in this path, you will see a partial solar eclipse.

Eclipse Zip Code Calculator

What will you see where you live? Check out this very cool solar eclipse calculator. (from Vox). Just punch in your zip code to find out WHEN it peaks and WHAT percentage of the Sun will be obscured by the Moon.

What’s the Difference Between a Total Solar Eclipse and Partial Eclipse?

Every solar eclipse involves the alignment of three celestial objects—Earth, Moon, and Sun. We all know that the Moon orbits the Earth, and the Earth orbits the Sun. When the Moon passes directly between the Sun and the Earth, you have a solar eclipse. All three objects are aligned. However, the alignment is not always perfectly straight.

Here’s a great explanation of the difference between a total solar eclipse and a partial eclipse shared by a student and Almanac fan, Sarah Pearson, who is a PhD student at Columbia University studying astrophysics. Check our her youtube channel “Sarah with Space” where she answers space-related questions!

A Total Solar Eclipse

For a total eclipse to take place, the Earth, Moon, and Sun are indeed perfectly straight. The Moon is directly between the Earth and Sun—and covers the entire disk of the Sun so that sunlight does not reach Earth. The Moon casts a shadow onto Earth and the sky becomes very dark as if it were night. A total solar eclipse is only visible from the path of totality, which is a small area on Earth. The people who see the total eclipse are in the center of the path or Moon’s shadow when it hits Earth. During totality, the Sun’s outer atmosphere (the corona) becomes visible.

What is a Solar Eclipse?

Partial Solar Eclipse

The second type of solar eclipse is a partial solar eclipse. The Earth, Moon, and Sun do not perfectly align. The Sun appears to have a dark shadow on only a small part of its surface.

Partial solar eclipses are quite common. They occur every few years. The difference between a total solar eclipse and a partial eclipse is like the difference between night and day. If you didn’t know a partial eclipse was happening, you might not even notice it. While astronomically interesting, the partial eclipse does not have that rare total darkness that you experience in the total solar eclipse.

If you do want to check out the partial solar eclipse, do NOT look at the Sun without proper filters. Do not use sunglasses. They will NOT protect your eyes! Read more about how to safely view the 2017 total solar eclipse without damaging your eyes

Annular Solar Eclipse

There is a third type of eclipse called an annular (ANN you ler) solar eclipse. This occurs when the Moon is farthest from Earth. Because the Moon is farther away from Earth, it seems smaller. It does not block the entire view of the Sun. The moon in front of the sun looks like a dark disk on top of a larger sun-colored disk. This creates what looks like a ring around the Moon.

During a solar eclipse, the moon casts two shadows on Earth. The first shadow is called the umbra (UM bruh). This shadow gets smaller as it reaches Earth. It is the dark center of the moon’s shadow. The second shadow is called the penumbra (pe NUM bruh). The penumbra gets larger as it reaches Earth. People standing in the penumbra will see a partial eclipse. People standing in the umbra will see a total eclipse.

The Path of the Total Solar Eclipse 2017

NASA has prepared an excellent Interactive Total Solar Eclipse Map displaying the Path of Totality as well as locations that will see partial eclipses. For a general idea of the eclipse’s path, see the simplified map, below. Click here for an enlarged view of the above map.

Map of the 2017 total solar eclipse by NASA.

Seeing the Total Solar Eclipse

If it happens to be cloudy in your area on August 21, or you are not in the path of totality, there are a couple options.

  1. Watch on Slooh:  Slooh is the market leader in live celestial event programming. They will be live streaming the entire Transcontinental Solar Eclipse from the moment the Moon’s shadow first touches Earth in the Pacific Ocean, then makes landfall in Oregon, before racing at supersonic speeds across the entire continental United States. The coverage takes place on Monday, August 21, 2017 at 8:30 AM PDT  |  11:30 AM EDT  | 15:30 UTC (International Times: http://bit.ly/2f6rp4B).  Watch here: https://www.slooh.com/
  2. Watch on NASA: Live video streams of the total solar eclipse will be available on NASA’s eclipse site.

Undoubtedly, many other Web sites will offer live coverage of the eclipse.

Of course, it is never too late to travel to the eclipse path. Though many campgrounds or hotels are booked, all you really need is an empty parking lot or an athletic field or cemetery!  The total solar eclipse happens in the middle of the day so lodging may be irrelevant if you’re in driving distance. The only requirement is to be located in the eclipse’s path. See the best places to watch the total solar eclipse.

For all your eclipse information, see the Almanac’s Total Solar Eclipse 2017 Guide!

Reader Comments

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Eclipse!

I GUESS i should pay more attention. I thought it was Sunday not MONDAY! Based on my results with the equipment I have I probably won't bother with the Speed Graphic just to view it. The Sony doesn't have the magnification I want but I was able to get the sun just not as clear as I had hoped.

Eclipse?

I used the Vox calculator which told me that for my zip code 67% of the sun would be blocked with the moon at about 2:47 pm EST. At about 2:36 the clouds parted enough to see the sun with my Speed Graphic, a Tele Peconar lens and the bellows out as far as it would go (no film just as a viewer) and never saw anything that would pass as an eclipse. I also used a Sony F828 camera with a 1000nm IR pass filter and never saw anything but a full circle of the sun.