Partial solar eclipse photo: UK

A wondrous annular or ring eclipse of the sun takes place on May 20, 2012 as seen from the southwestern U.S. – on May 21 according to calendars in Asia and Indonesia. For a comprehensive post about the annular eclipse, look here. This post will focus on the partial eclipse, which much of the world will be able to see. Given clear skies, all but the eastern part of North America can watch a partial eclipse of the sun in the afternoon hours on May 20. Much of eastern Asia and Indonesia will see the partial eclipse on the morning of May 21. Looking for eclipse times? Jump to the bottom of this post.

Map of May 20-21 partial and annular solar eclipse

Image credit: Fred Espenak. Click here for a larger map

Annular eclipse of the sun – China to Texas – on May 20 or May 21

Eye safety during solar eclipses

First, what happens on May 20/21? As seen on the map above, a partial solar eclipse can be viewed today (May 20 or 21 if you’re west of the International Dateline) from almost all over the North Pacific Ocean, much of North America, Greenland, eastern Asia and parts of Indonesia. The partial eclipse can be seen from a wide area that goes as far north as the Arctic and as far south as Indonesia and Mexico. Meanwhile, only a small sliver of the globe will be in a position to see the annular eclipse (the narrow red band extending from southeast China to the southwestern United States).

What is an annular eclipse? In an annular – or ring – eclipse, the moon crosses directly in front of the sun, much as it does during a total solar eclipse. But, at an annular eclipse, the moon is too far away in its monthly orbit around Earth to appear large enough in our sky to cover the sun completely. So, at mid-eclipse – instead of the moon covering the sun completely, as in a total eclipse, turning the sky dark and blotting the sun from view – in an annular eclipse a ring surrounds the moon silhouette. This dazzling ring is the outer edge of the sun. An annular eclipse is a partial eclipse in the sense that the moon never blots out the sun completely. At no time can you gaze at an annular eclipse without protective solar filters to prevent damage to your eyes.

What is a partial eclipse? In a partial eclipse of the sun, the moon’s distance from Earth isn’t so important. A partial eclipse differs from an annular eclipse only in that the moon doesn’t line up with the sun quite so directly, as seen from your vantage point. In a partial solar eclipse, the moon appears to take a bite out the solar disk. How big a bite? On May 20 (or 21 for those in Earth’s eastern hemisphere), that will depend on how close you are to the path of the annular eclipse on Earth’s surface – shown in the images above as that red central line (the one with circles inside it, indicating it’s the track of the moon’s shadow across Earth). The closer you are to that shadow track, the greater the partial eclipse you’ll see.

The eclipse starts at sunrise on May 21, 2012 in Asia, travels eastward across the North Pacific Ocean and ends at sunset on May 20, 2012 in North America – nearly six hours later. Strange that the date goes backwards? Yes, as the shadow path moves along over Earth’s surface, it crosses the International Date line, going east. In fact, midway between Asia and North America, the greatest eclipse happens at local noon, very close to the International Date Line.

We wish to remind you of the utmost importance of using proper eye protection when watching a partial or an annular solar eclipse.

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Annular eclipse of the sun – China to Texas – on May 20 or May 21

Watching the partial eclipse in North America

Because the eclipse happens in the late afternoon in North America, it’ll be to your advantage to find an unobstructed western horizon. The farther west you are in North America on the afternoon of May 20, the more of the eclipse that you will see. The U.S. East Coast will miss out entirely because the sun sets before the eclipse even begins.

Image credit: Tim Ebbs

Remember, it’s of the utmost importance to use proper eye protection whenever watching a partial or an annular solar eclipse. Click here to find out if an astronomical organization near you is hosting a public presentation of the event.

Eye safety during solar eclipses

When is the partial eclipse visible from my part of the world?

To know whether a partial or an annular eclipse is visible from your part of the world, and at what times, we provide links to two great resources. Click on this worldwide map, courtesy of the NASA eclipse web site, and scroll to your part of the world. Click at where you reside on the map to obtain eclipse times. Or go to this solar eclipse computer, courtesy of the U.S. Naval Observatory.

Keep in mind that both references give the times in Universal Time, so you need to convert from Universal Time into your time. For U.S. time zones, subtract 7 hours for Pacific Daylight Time, 6 hours for Mountain Daylight Time, 5 hours for Central Daylight time and 4 hours for Eastern Daylight Time.

How do I translate Universal Time into my time?

Find the time of the eclipse for you with the U.S. Naval Observatory’s eclipse computer. This solar eclipse computer gives times in Universal Time. In case the eclipse is cut off by sunset (in the Western Hemisphere), or by sunrise (in the Eastern Hemisphere), this solar eclipse computer gives the sunset or sunrise time.

Or find the time the eclipse for you with a different tool, an solar eclipse path map from NASA. As with the solar eclipse computer above, the eclipse path map gives times in Universal Time. It’s a nice tool, too, although it doesn’t give the times for sunset or sunrise, which you probably need for this eclipse. You can create a custom sunrise-sunset calendar here.

How do I translate Universal Time into my time?

Bottom line: North America, the North Pacific Ocean, Greenland, eastern Asia and parts of Indonesia will be able to watch the partial solar eclipse. The annular (ring of fire) eclipse will take place over a slice of the American Southwest, southeast China, far northern Taiwan and southeast Japan. If you live on the North American side of the Pacific, the eclipse will occur in the late afternoon hours before sunset on May 20, 2012. And if you live on the Asian side of the Pacific, the eclipse will be in the morning hours after sunrise on May 21, 2012.