Spectacular Sunset May Be on the Horizon : Astronomy: ‘Ring of fire’ solar eclipse will occur Saturday afternoon when the moon passes in front of the sun.

Southern California should have an extraordinary sunset Saturday because the moon will pass directly in front of the sun just as old Sol drops over the horizon.

This will be the second solar eclipse in this region in six months, but it will be quite different from the partial eclipse seen here July 11, which was a total eclipse over Hawaii and Baja California. The moon will not quite cover the sun, leaving a thin ring of light around the sun in what is called an annular eclipse.

Astronomers at Griffith Observatory have dubbed it the “ring of fire eclipse.”

If the weather cooperates, the view could be enchanting because it will combine a solar eclipse with all the colors produced by a sunset. However, a few clouds low on the horizon could block out the view entirely.

“It’s going to range from not seeing anything to seeing something that is extraordinarily beautiful,” said John E. Mosley, program supervisor at Griffith Observatory.

Because the sun will be very low on the horizon, and thus filtered by the Earth’s atmosphere, it is possible to “glance” at the eclipse without protective eyeglasses, Mosley said, but “I’m not recommending that.” The problem is that people tend to stare at an eclipse, not glance at it, and prolonged exposure could damage the eyes.

And because it is so low on the horizon, normal eclipse filters, such as welder’s glasses, will not work. The atmosphere works as a filter, and another dark filter would wipe out the view entirely, Mosley said. And welder’s glasses will absorb the orange rays of sunlight seen at sunset, so it would not be possible to see the sun at all.

The observatory has stockpiled orange filters that will protect the eyes while allowing enough light to pass through so that people can view the eclipse. The filters will be on sale for $5 at the observatory.

Homemade filters are not recommended, Mosley said, because “you never know what kind of light might get through.” The atmosphere on the horizon will absorb the ultraviolet radiation that can injure the eyes during an eclipse, but infrared rays will still get through and can cause serious damage to eyesight.

Solar eclipses occur somewhere in the world about once a year, but most eclipses are partial because the moon passes in front of only part of the sun. Sometimes, the moon covers the entire sun, producing a total eclipse.

The sun is 400 times larger than the moon, but it is also about 400 times farther away, so the two bodies appear as about the same size when viewed from Earth.

The moon’s orbit around the Earth is not perfectly circular, and neither is the Earth’s orbit about the sun. So sometimes the moon is not quite as large in the sky as the sun, and even if it passes directly in front of it, the moon’s image is too small to cause a total eclipse.

That produces an eclipse that is annular (ringlike). On Saturday, the moon will cover about 82% of the sun.

An annular eclipse generally is not as spectacular as a total eclipse because even a small part of the sun produces enough light to keep the sky from turning black.

The moon will begin to pass in front of the sun at 3:33 p.m., marking the beginning of the partial phase of the eclipse. Times will vary by a minute or so, depending on location, but the annular phase will start at 4:50.

Annularity will last five minutes, but the sun will set during that phase so it will not be visible for the entire period.

The annular phase will be visible from Malibu to Ensenada, Mexico, and from the mountains that form the eastern rim of the Los Angeles Basin. Viewers will need to have an unobstructed view of the Pacific to see the sun as it drops below the horizon.

Griffith Observatory expects to have a couple of dozen telescopes set up, but officials there are expecting such large crowds that visitors are encouraged to bring binoculars. The filters provided by the observatory will work on binoculars and small telescopes.

Because large crowds are expected, the road to the observatory will be closed. Shuttle buses will run throughout the day, beginning at 10:30 a.m., between the observatory and lower parking lots. The observatory will offer three programs on the eclipse--at noon, 1:30 p.m. and 7:30 p.m.

The Mt. Wilson Observatory in the San Gabriel Mountains will also be open for the eclipse. At 5,700 feet, the observatory should provide a view from above the smog, but winter storms can close roads at any time. There will be a lecture at the Mt. Wilson Museum at 2 p.m. Several small telescopes will be set up at the observatory for viewing.