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Ring of Fire : Sun, Moon Will Sink Into the West on Jan. 4 in Rare, Spectacular Eclipse

December 19, 1991| Jerry Schad | Jerry Schad is an outdoor enthusiast, educator and author of books on hiking and cycling in San Diego County.

Back in the 1960s, astronomy was a consuming passion of mine. I looked forward with keen anticipation to four "far-future" events: the return of Comet Halley in 1985; the total solar eclipses of Feb. 26, 1979, and July 11, 1991 (both viewable from places not far from my native California), and the annular solar eclipse of Jan. 4, 1992. To date, I've had the pleasure of witnessing three of these events at just the right places and times, under beautifully transparent skies.

Today and tonight, the waxing gibbous (nearly full) moon continues on its appointed path around the Earth, bound toward an inevitable rendezvous with the sun just 16 days from now. At 3:35 p.m. Saturday, Jan. 4, the new moon's dark silhouette will start to take a "bite" out of the blazing solar disk as seen from San Diego County. The obscuration will increase until the moon lies more or less centrally over the sun about 4:49 p.m. By rare coincidence, this moment will be simultaneous with the local setting time of both the sun and the moon.

Since the moon on Jan. 4 will lie near the farthest point in its orbit, and therefore appear relatively small, the obscuration will not be total. No pearly solar corona will be visible. Instead, an intensely bright, thin ring of the sun's photosphere will remain visible. A "ring of fire" (as astronomers at Griffith Observatory in Los Angeles are billing this event), reddened and distorted by the atmosphere, will sink into the Pacific Ocean.

For any given spot on Earth, annular (meaning "ring-like") solar eclipses occur about once every 250 years. Annular eclipses occurring at sunset are much more rare--happening roughly once every 20,000 years for any given locality. This particular annular eclipse begins at sunrise in the Western Pacific and ends along a 200-mile-long, 100-mile-wide area covering the coastal strip from Los Angeles to Ensenada. The center line of the path of annularity passes over Encinitas and Palomar Mountain.

Since this eclipse is actually a type of partial solar eclipse, the usual concerns about safe viewing apply. Until the sun gets very close to the horizon, it can only be viewed directly in a safe manner through appropriate sun-viewing filters--a No. 14 arc-welder's filter or the special aluminized filters that have been sold in this area for the purpose of viewing last July's solar eclipse. Don't stare at the high-angle sun for long periods, even with the use of these filters.

Indirect viewing methods are better: You can use a sheet of aluminum foil, punched with one or more pinholes, to project an image or images of the sun upon any light-colored surface a few feet away.

As the sun sinks toward the horizon, it will fade an unpredictable amount and also become reddened due to atmospheric haze or smog. The rate of dimming will depend on local conditions.

As you would view any normal sunset with the naked eye, you can at least briefly glance at the eclipsed sun as long as it is either just above or on the horizon. Heavy smog or thin clouds might permit comfortable viewing even before the sun reaches the horizon. Optical aids such as binoculars or telescopes may be used with care as long as the sun is dim enough to view comfortably with the naked eye.

Take brief looks only; infrared radiation (radiant heat) from the setting sun may still be intense enough to damage the retina of the eye if you stare for a long time at a bright solar image.

The ring effect begins at approximately 4:45 p.m., depending on your exact location. If the horizon is perfectly clear, you'll enjoy three to four minutes of annularity before the sun disappears.

Weather prospects for Southern California in early January are not ideal. On average, only about 35% of January afternoons have cloudless or nearly cloudless skies. About 15% of January days get rain.

Under the most likely scenario of partly cloudy conditions, you may want to try to escape adverse conditions. Be prepared to head north or south along the coast to outflank slow-moving banks of high clouds. Be prepared to escape low clouds by moving inland or up into the mountains. The mountains, however, sometimes generate their own clouds, in which case you would want to stay near the coast.

Where will I be during the eclipse? Probably at one of the sites noted on the map printed here. In the meantime, let's invoke the powers that be to grant us clear skies and a magnificent spectacle on the 4th.

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