Annular Eclipse of the Sun: Sunday, May 20th, 2012

Warning: Never view an eclipse, nor any other sun-related phenomenon, without using adequate eye protection.

On Sunday, May 20th, 2012, there will be an annular eclipse of the sun, beginning just around 5PM U.S. Eastern Daylight Time (EDT). The eclipse will begin in eastern China and Japan, tracing a “great circle” path across the northern Pacific, reaching the Aleutian Islands, then portions of the northwestern and southwestern United States, and finally terminating around Lubbock, Texas.

Annular Eclipse of the Sun

Unfortunately, those of us here in the eastern United States won’t be able to see any of this, but I think it’s still significant to know that this phenomenon is occurring, and at what time, and that others will be viewing and photographing it. And if you do happen to be in a good location to experience some portion of this eclipse, don’t attempt to view it directly without adequate eye protection (e.g., #14 welder’s glass, or equivalent sun filters on your telescope or binoculars). And if you cannot acquire adequate eye protection, just keep in mind that you can still enjoy your temporary state of ambient partial darkness for what it is, without having to look toward the sun.

A solar eclipse is really nothing more than a manifestation of the new moon. During the new moon phase, the moon is in a position between earth and sun, and usually not visible, simply because the moon’s at too close an angle to the sun (relative to the earth) to reflect any sunlight back to earth, while the sun’s glare also makes it impossible to catch a glimpse of the darkened moon.  This phenomenon occurs once per synodic (lunar) month. And the new moon is invariably followed by a slivered crescent moon, visible right at sunset, as the moon begins its new cycle.

Schematic of Solar Eclipse

But every once in a while, the new moon is in such a position that its shadow touches some part of the earth, and some portion of the darkened moon becomes visible at that location. This is an eclipse. If the moon covers only part of the sun, it’s called a partial eclipse. But when it covers the sun completely, it’s called an annular or full eclipse. Since the moon’s apparent diameter is slightly smaller than the sun’s, this results in the so-called “ring of fire” or “penny in a nickel” effect. In ancient times, people were well aware of the moon’s normal phases, but eclipses were unexpected, and often caused great panic, as many believed that the new moon had just devoured the sun, or was otherwise portending doom.

On the evening of Sunday, May 20th, 2012, the new moon officially occurs at 7:47PM EDT, just thirteen minutes before the moon sets at 8:00PM EDT, while sunset is about 8:04PM EDT. These times shouldn’t be surprising, since sun and new moon will be transiting the sky together, the sun just ever so slightly catching up with the moon, for much of the day. For example, in my own location, the moon crosses the meridian (directly over head) on Sunday at 12:43PM EDT, while the sun crosses at 1:00PM EDT. Note that this is the true noon hour (12:00PM EST), only adjusted ahead one hour for day light savings (1:00PM EDT).

An initial, partial eclipse begins at 4:56PM EDT, with annularity beginning about one hour later. The maximum annular eclipse will occur at 7:53PM EDT, just before the sun sets for us here in the eastern United States. And the eclipse will end completely at 10:49PM EDT. Of course, as I’d stated earlier, none of this will be visible to any of us here in the east, but it’s still good to know what’s transpiring, and when.

So, happy viewing, to those of you in good viewing locations. And remember that eye protection!

 

About John Poole

My interests include historic homes, architectural preservation and restoration, improving the energy performance of old houses, and traditional timber frames.
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2 Responses to Annular Eclipse of the Sun: Sunday, May 20th, 2012

  1. I was disappointed not to see it here in Santa Barbara. A woman at the park insisted it would come here, but she was WRONG.

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