Sky and Telescope - May 2012 - (Page 50)

OBSERVING

Celestial Calendar

The May 20th Annular Eclipse
Plan now what you’ll be doing on this very special Sunday afternoon.

People in all but the easternmost parts of the U.S. and Canada have a red-letter day coming up Sunday, May 20th. Late that afternoon the Sun, lowering in the western sky, will undergo at least a partial eclipse. The eclipse will become annular, with the Sun turning into a brilliant ring around the Moon’s dark silhouette, for parts of southern Oregon, northern California, Utah, Arizona, New Mexico, and a bit of Texas, as shown below and at the bottom of the facing page. This is the ﬁrst central solar eclipse (meaning total or annular) to cross the United States since 1994. Untold numbers of people are planning to park themselves near the centerline for this grand event. A much larger number across the continent will enjoy the weird spectacle of a partial solar eclipse low in the sky. The eclipse will still be in progress at sunset in the region between the red lines below, with the Moon intruding onto the reddened, atmospherically distorted Sun.
Nearly all North America gets at least a partial eclipse, with the Moon taking a big bite out of the Sun. The eclipse will still be in progress at sunset for much of the U.S. and Canada. That will make it scenic indeed, but you’ll need a clear horizon to the west-northwest.

The May 20th eclipse will appear very similar to previous eclipses in saros cycle 128, such as this one in 1994, because the geometric circumstances are almost the same. Author Fred Espenak photographed this sequence one saros ago.

Pa tial/Annula Sola Eclip Partial/Annular Solar Eclipse Partial/Annular Solar Eclipse lar lar lips ips Ma May 20 May 20
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North Americans will see the tail end of this eclipse. Its annular part begins at sunrise along the southern coast of China (where the local date is May 21st), then crosses parts of Japan, including Tokyo on the centerline. It then speeds across the empty North Paciﬁc through much of the day, before making landfall on the rugged California-Oregon coast at 6:24 p.m. Paciﬁc Daylight Time. There the Sun will be a good 22° above the western horizon, and annularity will last 4 minutes 47 seconds as seen from the centerline. The path of annularity continues southeast with the Sun sinking lower. Residents of Albuquerque see the annular eclipse just 5° above the horizon. Western Texas near Lubbock is a particularly interesting location for photographers, because there the annular phase will occur just before sunset.

What to Watch For
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Eclipse complete before sunset No eclipse More than half of eclipse before sunset Less than half of eclipse before sunset

“Annular” means “ringlike,” and the ring of the Sun at the middle of this eclipse will be unusually thick. The Moon will be practically at the apogee of its orbit, appearing almost as small as it gets, so it will span only 94% of the Sun’s diameter. This means only 88% of the Sun’s surface area will be blocked during annularity. The result will be less change in the quality of the daylight than you might expect. Thin clouds would dim the day more. The exposed surface of the Sun itself will remain blindingly bright — literally — so anyone viewing any part of this eclipse, total or annular, must use the

50 May 2012 sky & telescope

Table of Contents for the Digital Edition of Sky and Telescope - May 2012

Sky and Telescope - May 2012
Table of Contents
Spectrum
Letters
75, 50 & 25 Years Ago
News Notes
Saturn’s Raging Superstorm
Stars Above, Earth Below: Astronomy in National Parks
The Remarkable Case of Comet Lovejoy
In This Section
May’s Sky at a Glance
Binocular Highlight
Planetary Almanac
Northern Hemisphere’s Sky
Sun, Moon, and Planets
Celestial Calendar
Exploring the Solar System
Deep-Sky Wonders
Going Deep
S&T Test Report
New Product Showcase
Telescope Workshop
Planetary Imaging with Your DSLR Camera
Gallery
Focal Point

Sky and Telescope - May 2012