Thursday 17 May 2012

For US observers: Annular or ring eclipse on Sunday May 20




Those living along a narrow track from northern California to the Texas panhandle will have a chance to witness a special kind of eclipse of the sun. The sky won’t turn dark, and stars won’t pop into view, because this eclipse is essentially partial. At no time will the moon cover the sun completely, and thus you will need to use special filters, or an indirect viewing system, to see it. At mid-ecipse, though, if you’re equipped to observe, you’ll see an awesome sight. The outer rim of the sun’s body will appear as a brilliant ring completely encircling the black moon silhouette. Hence the name annular eclipse, from the Latin word annulus meaning ring.

As the solar eclipse on May 20th progresses, its partial and annular phases will look very similar to this eclipse on May 10, 1994

Americans are seeing the tail end of this eclipse. It begins at sunrise along the southern coast of China – across the International Dateline from us in the US – where the date is May 21. The eclipse sweeps across Japan and Tokyo residents will be on the centerline. The eclipse then speeds across the North Pacific through much of the day before making landfall on the California-Oregon coast in the late afternoon of May 20, according to US clocks and calendars.


The path of annularity runs across parts of southern Oregon, northern California, Nevada, Utah, Arizona, New Mexico and the Texas panhandle. But those outside this path will see an eclipse, too. It’ll be an ordinary partial eclipse of the sun, whose depth will depend on how close you are to the central eclipse track.

 

Nearly all North America gets at least a partial eclipse on May 20th, with the moon taking a big bite out of the sun. The eclipse will still be in progress at sunset for much of the US, Canada, and Mexico. What to expect from North America. The sun will be moving down the afternoon sky when – with your solar filter or indirect view method – you perceive that a dark dent has began to intrude into one edge of the solar disk. As the eclipse progresses, depending on your location, the sun will eventually become a fat crescent – or, for the western half of the North America, a thin crescent.


Traveling along its monthly orbit around the Earth, the moon will pass directly in front of the sun’s disk. But it will be too far from Earth in its orbit to cover the sun completely. That’s why this eclipse is annular, instead of total.


People in the western US will see the entire eclipse from beginning to end before sunset. In the central US, the sun will set while the eclipse is still in progress. Some of the tips are as follows:-

Look for a weird and spectacular sunset scene just above the west-northwest horizon. Get your camera ready for a great photo opportunity!

The further east you are in the United States, the earlier in the eclipse the sun sets for your location. The US East Coast misses out completely. There, the sun sets before the eclipse begins.

This will be the first “central” solar eclipse (meaning total or annular) to cross the United States since 1994.

What to watch for Remember, this is essentially a partial eclipse. The moon will be at apogee – farthest from Earth for the month of May 2012 – two weeks, or half an orbit, after the moon was a “supermoon” at perigee at full moon on May 5.


Only 88% of the sun’s surface area will be blocked during annularity. The visible surface of the sun – in a fiery ring around the moon – can literally blind you. So be sure to watch indirectly, or with special filters. Do not look at the sun directly without eye protection at any time during this eclipse.


The sky will not grow dark, but – if your sky is very clear – you should see that the sky is a darker, deeper blue than normal at mid-eclipse. Look for the brightest planet, Venus, at mid-eclipse. It’ll be shining east of the sun by about two fist-widths at arm’s length. Jupiter and Mercury are up there, too, but they are fainter and so will be harder to see. They’re on the other side of the sun by about a quarter and a third as far, respectively.








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