WASHINGTON: At sunrise in some parts of China and by sunset in the western United States, a partial solar eclipse is set to slink across the Earth on May 20 and 21.
Depending on where people are in the eclipse's path, some may be able to witness an annular eclipse in which the moon blocks out all but a ring of the Sun's light.
Others will see the Sun as a crescent, partially obscured by the moon, for a period of around four to five minutes.
"The desert areas of Nevada, southern Utah and northern Arizona may be the best (for viewing) if they have the greatest chance of clear skies and the eclipse takes place low in the sky over a dramatic landscape," said Alan MacRobert, editor of Sky and Telescope magazine.
According to historical cloud data, China and Japan may be out of luck since a high likelihood of gray skies would block the view of the Sun.
"Unfortunately this is monsoon season, and the weather prospects are supposed to be poor in southern China," MacRobert told AFP, but nevertheless urged residents to check local forecasts for updates.
"China and Japan don't look to be very lucky for this. It would take quite a stroke of luck to get a clear sky."
Of course, no one should look directly at the eclipse due to the risk of permanent eye damage. Even sunglasses are not enough to protect eyes from the glare.
Instead, experts say a safe solar filter, such as a #13 or #14 rectangular arc-welder's glass or an astronomer's filter made specifically for Sun viewing are the best options.
The path of the annular eclipse will span "a 240 to 300 kilometer-wide (150-185 mile) track that traverses eastern Asia, the northern Pacific Ocean and the western United States," according to the US space agency.
The eclipse begins at sunrise in southern China at 2206 GMT on May 20, which is May 21 local time, and swiftly travels eastward to the southern coast of Japan, NASA said.
"Tokyo lies 10 kilometers (six miles) north of the central line. For the over 10 million residents within the metropolitan area, the annular phase will last five minutes beginning at 22:32 GMT (on May 21 local time)," said NASA.
The shadow then embarks on a 7,000 kilometer-long (4,350 miles) Pacific ocean voyage that will endure for about two hours, skimming just south of Alaska's Aleutian Islands.
The eclipse will reach the coastlines of southern Oregon and northern California at 0123 GMT May 20 local time, and it should be visible in Nevada, Utah, New Mexico, Arizona and Texas.
The East Coast of the United States will not see any of the eclipse because the Sun will have already set.
MacRobert said such annular eclipses take place on average about once a year somewhere in the world, though they are not always visible to large numbers of people.
The next time the Earth will witness a total eclipse of the Sun, a more dramatic event than a partial or annular eclipse, will be August 21, 2017.
Further details: http://eclipse.gsfc.nasa.gov/SEmono/ASE2012/ASE2012.html
Safe viewing tips: http://www.skyandtelescope.com/observing/home/Safely-View-the-Upcoming-Eclipse-and-Transit-150863835.html
by Kerry Sheridan