Jimmy Westlake: May’s magnificent ring eclipse
April 30, 2012
Get ready, because here it comes.
Not since May 10, 1994, has a central eclipse of the sun been seen from the 48 contiguous United States. It has been a long eclipse drought, but come May 20, folks living in the southwestern U.S. will have a ringside seat for a spectacular annular eclipse of the sun. This eclipse is an annular, or ring eclipse, because the moon will be a little too far from Earth in its elliptical orbit to completely cover the sun. Instead, a thin annulus — or ring — of sunlight will surround the moon when it is centered on the solar disk.
The 150-mile wide path of annularity enters the continental U.S. late on the afternoon of May 20 in northern California and it ends at sunset near Lubbock, Texas. To see the complete, unbroken ring of sunlight surrounding the moon, one will need to travel a little south of Colorado, close to Page, Ariz., or Albuquerque, N.M.
For Northwest Colorado, the eclipse will be off center, and only 85 percent of the sun will be covered. The eclipse begins at 6:23 p.m. when the moon takes its first little nibble out of the lower right edge of the sun's fiery disk. Maximum eclipse occurs at 7:30 p.m. when the moon will have reduced the sun to a thin crescent shape, only 8 degrees above the west-northwest horizon. The partially eclipsed sun will set at 8:22 p.m.
At no time on May 20 will the sun be completely hidden from view and safe to observe without a proper solar filter. Glancing at the sun any time, even for a brief moment, can cause severe eye damage and possibly blindness. Viewing the eclipse safely will require holding a No. 14 welder's glass or an approved aluminized Mylar filter in front of your eyes. Eclipse glasses made from this Mylar material are available commercially from many sources of telescope and photography equipment. Ordinary sunglasses provide absolutely no protection against the sun's harmful rays, so don't try it.
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Any tiny, round hole will project a safe image of the sun onto a white card. Try holding a colander or spaghetti strainer up toward the eclipsed sun to see dozens of little eclipse images projected onto a piece of white poster board held behind.
If you own a telescope or even a pair of binoculars, you can use them to project an image of the eclipsed sun on a white card. Just remember to use extreme caution and never place your eye up to any optical device aimed at the sun. Also, never leave your telescope unattended while aimed at or near the sun.
This month's annular eclipse is just a warmup for the spectacular total eclipse of the sun coming our way in August 2017. Cutting a swath right across the state of Wyoming, this long-awaited eclipse will be the first total eclipse of the sun for the 48 contiguous states since February 1979.
Jimmy Westlake teaches astronomy and physics at Colorado Mountain College's Alpine Campus. Check out Westlake's astrophotography website at http://www.jwestlake.com.