Half the people trying to view Saturday's lunar eclipse will miss it because they'll forget to look up.
Honest, says John Mosley, a Griffith Observatory astronomer who says the No. 1 piece of advice he gives is "remember to look up." If you don't forget, the rest is easy.
Saturday's total lunar eclipse is the second and last of the year -- the first was in May. Another one won't appear here until next October. After that, those of us in the U.S. will have to wait until March 2007.
Viewing the eclipse is a no-brainer, Mosley says. Compared to the blink-and-you'll-miss-it quality of meteor showers, a total eclipse is a relatively long event that invites leisurely viewing. And you don't need a telescope or binoculars -- although they'll help bring out the color during the eclipse's later stages.
An eclipse occurs when the Earth is aligned exactly between the sun and the full moon. As the moon moves through the shadow of the Earth, it darkens for several hours. The dark central shadow on the moon is called the umbra and the lighter shadow surrounding it is the penumbra.
In Los Angeles, the eclipse will get underway right at sunset, at 4:51 p.m., when the moon begins to rise in the eastern sky. At that point, it will already be mostly shadowed.
A mere 15 minutes later, it will seem to disappear during the totality phase. The moon won't reappear until about 5:30 p.m., when it begins to shimmy out of the umbra.
If weather permits, the most dramatic view will be between 6 and 6:30 p.m., as the moon emerges from the Earth's shadow, its crescent shape thickening each minute.
Total escape from the umbra will occur at 7:04 p.m. By 7:30, the show will be pretty much over, although the moon won't completely exit the penumbra until 8:21 p.m.
The big draw is the potential for a color show. When the moon is about one-third out of the umbra, it could appear rosy red or as coppery as a penny, similar to the inspiring smog-tinged sunsets to which Angelenos are accustomed.
The brilliant hues are caused by the Earth's dense atmosphere, which acts like a lens and bends sunlight before it reaches the moon, says Patrick So, a Griffith Observatory astronomer. Any dust or smoke particles in the atmosphere will filter out all colors except red.
This coloration is hard to predict because there's no telling what kind of particles will be in the air at the time of the eclipse.
For example, a wildfire a day or two before could color the moon quite vividly -- similar to the way the smoke from the fires painted the sun various shades of pink. A volcanic eruption anywhere on Earth also would add to the color fest.
Eclipse watchers in the L.A. area need only find a comfortable spot with an unobstructed eastern horizon. The Griffith Observatory is setting up telescopes, along with the Los Angeles Sidewalk Astronomers, at the Observatory Satellite (near the Los Angeles Zoo parking lot), which is serving as headquarters while the main observatory undergoes renovation.
Although the view might not be the best because of trees and the moon's low position, Mosley expects to be swamped with eclipse observers.
For those looking to capture the moment, Griffith Observatory photographer Tony Cook recommends using 400 ISO film, or keeping it simple by using a digital camera that lets you see what you're getting.
Photos shot on the West Coast probably won't be as vivid as those on the East Coast, where the eclipse will occur higher up in a darker sky.
Because the brightness of the moon is so unpredictable during an eclipse, the trick to getting a good photo is to shoot a variety of images throughout the event, using different exposures -- the idea being that something will turn out.
During the last eclipse, some amateur photographers at Griffith Observatory with no experience shooting the night sky ended up with "really decent images," Cook says.
For higher-quality photos, try using a tripod to keep the camera as still as possible, and a cable release to snap the images by remote. Some photographers even hold their digital cameras up to a telescope's eyepiece to magnify the image.
During an eclipse, Cook recommends taking shots every few minutes using different shutter speeds; be sure to take some with the shutter kept open for several seconds.
If you don't get a keeper, there's always next year. Or 2007.
To e-mail Julie Sheer or read her previous Outdoors Institute columns, go to www.latimes.com/juliesheer.
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Catch the vanishing act
Griffith's Observatory Satellite facility is in the northeast corner of Griffith Park and will be open for free public viewing from sunset until 9 p.m.
Park in the Los Angeles Zoo parking lot and cross the street south to the satellite. For more information, call (323) 664-1181.
A free clinic on viewing and photographing eclipses is being staged at 7 p.m. Thursday by Adventure 16's San Diego store, 4620 Alvarado Canyon Road.
For more information, check out www.adventure16.com/events or call (619) 283-2374.