Sunset of a Lifetime

Eclipsing even those picture postcard-perfect sunsets of San Diego, the most spectacular sunset to grace this coastal city for thousands of years is expected on Saturday.

Weather depending, of course.

In Southern California’s second solar eclipse in six months, the moon will slide in front of the sun just as the sun drops to the western horizon. For astronomical reasons, the moon will not quite cover the sun, leaving a thin ring of bright light around the sun in what is called an “annular eclipse.”

If the weather cooperates, the sky will show a fiery solar eclipse combined with all the iridescent colors produced by a sunset. However, clouds scudding across the horizon could block the view entirely.

“It may not be the best eclipse ever, but I can promise it’ll be a sunset you won’t forget,” said Dennis Mammana, the resident astronomer at the Reuben H. Fleet Space Theater & Science Center in San Diego.

“That time of day, the sky should be filled with bright shades of red, orange and gold,” Mammana said.

Unless, that is, the sky is filled with gray storm clouds. Dan Atkin, meteorologist for the National Weather Service in San Diego, said there is a chance patchy clouds from a storm predicted to hit San Diego today will be lingering on the day of the eclipse. Following the rain clouds that washed San Diego last weekend, the new storm is likely to be more intense and will weaken by sundown Saturday, “but it’s still a little bit iffy if it’s going to be completely clear,” Atkin said.

The height of the eclipse should occur at 4:53 p.m., when the sun is low on the horizon.

Because it will be filtered by the earth’s atmosphere, it will be possible to sneak a peek at the eclipse without eye protection, astronomers said. But Mammana added that unprotected looks were not recommended because people tend to stare at an eclipse, not just peek, and prolonged exposure could cause eye damage.

Normal eclipse filters, such as welder’s glasses, will not work for this eclipse because the atmosphere also works as a filter and another dark filter would simply obscure the view, astronomers said.

Homemade filters are not recommended, either, as the protection they offer is uncertain, astronomers said. The Fleet science center at Balboa Park has stockpiled special $3.95 hand-held filters that will protect the eyes while still allowing enough light to view the eclipse and the spectacular shades of sunset, spokeswoman Sally Buckalew said.

A solar eclipse occurs somewhere on earth two to five times a year. During its 28-day orbit of the earth, the moon occasionally passes in front of the sun, producing an eclipse on earth.

Most eclipses are partial because the moon passes in front of only part of the sun.

Upcoming partial eclipses visible in San Diego will be on May 21, 1993; May 10, 1994; Feb. 26, 1998; and Dec. 25, 2000, according to the Fleet Center.

Since eclipses are unusual, it’s even rarer when an eclipse is linked to a sunset. The last sunset eclipse visible in Southern California was Jan. 5, 1647, Buckalew said. The next sunset eclipse visible here, she said, will be about 20,000 years from now.

Sometimes, the moon covers the entire sun, producing a total eclipse. That’s what happened last July 11 for viewers south of California, in places such as Hawaii and Mexico. Seen from Southern California, however, that eclipse was only partial.

Astronomers can predict--or backdate--partial and total eclipses because the motions of the moon and earth repeat themselves every 6,585 days. An annular eclipse, also easily predictable, involves just another few variables.

The sun is 400 times larger than the moon. But, at 93 million miles from earth, it is also about 400 times farther away than the moon, which lies about 240,000 miles from earth. That’s why the two bodies appear about the same size when viewed from the earth.

However, the moon’s orbit around the earth is not perfectly circular, and neither is the earth’s orbit about the sun.

During an annular eclipse, like the one that will occur Saturday, the moon lies farther in its orbit from earth, and the sun closer--making the sun appear to loom larger and the moon smaller.

As the moon passes in front of the sun, it does not cover it completely, leaving a ring of sunlight around its edge. That ring is called an “annulus.” On Saturday, the moon will cover about 91% of the sun, the Fleet center said.

An annular eclipse generally is not as awe-inspiring as a total eclipse for the simple reason that even a small part of the sun produces enough light to keep the sky from turning black, as it does during a total eclipse.

In addition, during a total eclipse, the moon blocks out so much sunlight that it is possible to see the sun’s atmosphere, called the corona, and the violent flares and eruptions on the solar surface. During an annular eclipse, the corona is too dim to be seen.

On Saturday, the moon will begin to pass in front of the sun’s lower edge about 3:35 p.m.. As the sun sinks in the sky and the moon rises in front of the sun, the moon will block more and more sunlight. The sun should appear orange by 4:15 p.m., the Fleet center said.

Times will vary by a minute or so, depending on location, but the annular phase--when the moon’s entire silhouette can be seen inside the sun’s disk--will start about 4:50 p.m., the center said. The reddened sun will appear distorted because of uneven atmospheric refraction.

Mid-eclipse will occur at 4:53 p.m. If the sky is clear, watchers at the beaches and mountains will be able to see a distorted, reddened ring of sunlight dropping into the Pacific Ocean, the Fleet center said.

At 4:56 p.m., the sun will set, and the eclipse will end.

From start to finish, the entire eclipse will last about 90 minutes. The best time to watch, astronomer Mammana said, will be the last 10 minutes.

The annular phase will be visible from Malibu to Ensenada. Because the eclipse falls on a Saturday, viewing crowds could be large, San Diego County park officials said, cautioning eclipse enthusiasts to arrive early at beach or mountain viewing spots.

Virtually any beach will do to watch, officials said. In North County and East County, recommended high spots include Black Mountain, Mt. Laguna and Palomar Mountain State Park.

Beginning at 3:30 p.m. Saturday at Palomar Mountain State Park, astronomer Jim Rickard will be available at Boucher Point within the park to talk about the eclipse and answer questions.

Ken Smith, the park’s chief ranger, said only handicapped visitors will be allowed to park on top of the point, about 5,000 feet high. Visitors may drive to the top to drop off passengers or camera equipment but must park down below, he said.

Smith cautioned visitors to remember that it’s likely to be cold and breezy on top of the point--especially when the sun goes down.

Viewing the Annular Eclipse

Why It Occurs

An annular eclipse occurs when the moon is so far from the earth that its umbra (or shadow) doesn’t reach the earth. And the sun’s corona, by the sun’s own light, is not visible on earth.

1. San Onofre State Beach: 3 miles of blufftop viewing sites just south of the Orange County line. 2. Boucher Hill overlook. Palomar Mountain State Park. 3. Roadside turnouts along East Grade Road on Palomar Mountain. 4. Blufftop viewpoints along Neptune Avenue in Encinitas and Leucadia. 5. Woodson Mountain: Hike 2 miles up paved service road from Highway 67 to summit. 6. Cuyamaca Peak: Hike 3 miles up paved service road from Paso Picacho Campground in Cuyamaca Rancho State Park. 7. Blufftops near Del Mar. 8. Black Mountain: Hike 2 miles up north side to summit. 9. Iron Mountain: Hike 3 miles from Poway Road/Highway 67 intersection to summit. 10. Glider Port. 11. Scripps Coastal Reserve: Short walk to top of cliffs off La Jolla Farms Road. 12. Soledad Mountain. 13. Cowles Mountain: Hike 1.5 miles up road on east side or up the trail on south side. 14. Sunset Cliffs. 15. View Point on eastbound Interstate 8, 5 miles east of Alpine. 16. Roadside turnouts near Mile 21 on Sunrise Highway. 17. Whale-watching overlook at Cabrillo National Monument.