Thursday, October 21, 2004
With three total lunar eclipses occurring in the past year, sky watchers may be stifling yawns to hear that another eclipse is due to happen Wednesday.
"They are common but no less beautiful," said Colorado Mountain College astronomy professor Jimmy Westlake. "They may seem a little ho hum, but we won't see another one until March 3, 2007."
Calendars list the eclipse as happening Oct. 28, Greenwich Mean Time, but Colorado will experience the eclipse Oct. 27.
Anyone who can fight the ennui long enough to look up will be rewarded with a nicely timed eclipse that will happen early in the evening. The sun sets at 6:15 p.m. Wednesday, which means it will be completely dark by 7:14 p.m. when the moon starts to disappear behind the shadow of the Earth.
"When the moon rises, there will already be a little bite missing from the lower left edge," Westlake said. That bite will grow during the next hour and nine minutes. The eclipse will reach totality at 8:23 p.m. In all, the eclipse will last three hours and 40 minutes.
"Not everyone will watch the entire thing," Westlake said. "But I will, and other astronomy nerds will.
"Others should go outside at about 8 p.m. to watch the last sliver of moonlight disappear."
Like Westlake, whose photos often are featured on the Astronomy Picture of the Day Web site, viewers may enjoy attempting to photograph the eclipse.
Cameras will need the ability to take a time exposure, Westlake said. "A point and click won't capture the eclipse." Zoom lens, tripod and cable releases also are needed.
"You can get an image with a standard lens, but it will be a tiny little image," Westlake said. During the partial phases of the eclipse, photographers should shoot at 1/60 or 1/125 of a second. During totality, photographers can shoot one-second to 30-second exposures.
"That will allow you to record the faint red color on the moon," he said.
Viewers will need a view of the southeastern sky, with no trees, mountains or city light obstructing views of the moon when it is low on the horizon.
An eclipse only can happen on a full moon when the Earth and the moon and sun are all along the same line. The moon passes directly behind the Earth into the Earth's shadow.
"It would disappear completely if it weren't for sunlight streaming through the Earth's atmosphere," Westlake said. "The light that comes through is orange or red in color.
"In a way, it's similar to alpenglow. Even after the sun has gone down, there is still that light, the alpenglow light."
Whenever there are volcanic eruptions, the color of the eclipse gets redder. Astronomers are unsure about the effect of Mount St. Helens.
"Every eclipse is a little different," he said.
While people are looking up, they also may enjoy the changing star visibility as the moon disappears. At first, the Milky Way will be washed out, but during totality, observers will see a red moon hanging in the sky with the Milky Way streaming passed. As the eclipse ends, the Milky Way will be washed out again.
For more information about the eclipse and for a gallery of photos saved after the eclipse, possibly including some images by Westlake if the weather is good, visit www.spaceweather.com.