Total lunar eclipse tomorrow (thursday) night

[Rokenn]

Total lunar eclipse Thursday evening

Moon expected to glow eerie orange or red as Earth blocks direct sun for nearly an hour

David Perlman, Chronicle Science Editor Wednesday, May 14, 2003

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Sky watchers should see the moon change color dramatically Thursday evening as a total lunar eclipse becomes briefly visible over Northern California.

For 53 minutes, the sun, the Earth and the moon will be lined up as the moon passes through the Earth's dark shadow, and vivid colors -- perhaps orange and bright red -- will paint the moon's face, the result of sunlight refracting through the Earth's atmosphere.

"Even for a few minutes, it can be a truly eerie sight," said Robert Naeye of the Astronomical Society of the Pacific. "When the moon moves deep into the darkest part of the Earth's shadow, you can never predict just what colors it will show."

The weather forecast for Thursday night is for breezes and mostly clear skies. Even if some thin clouds do cross the moon's surface, "that can really be a showstopper as you watch the wisps of cloud drifting by the moon like veils," Naeye said.

Time is a little against us on the West Coast. When totality begins at 8:14 p.m. Thursday, it will still be daylight, and the moon will just be rising in the east while the sun sets in the west. So it will still be too bright to get a good view at first.

Fortunately, totality will last until 9:07 p.m. For about 10 minutes before then, it should be dark enough for the moon's totally eclipsed face to display its spectacular colors, even though the rising moon will still be low on the southeastern horizon, Naeye said.

After that and until about 10:30 p.m., the moon will gradually lighten as it moves out of the main part of the Earth's shadow, called the umbra. But that event should be a spectacle worth watching, too, Naeye said.

The colors of a moon in total eclipse -- sometimes a deep blood-red -- are caused by Earth's atmosphere, which filters out the sun's blue light while it bends red and yellow rays onto the moon's face.

Dust and ash cluttering Earth's upper atmosphere from recent volcanic eruptions or forest fires also can change the moon's colors, but because no major volcanoes have erupted recently and the atmosphere is relatively clear, Naeye is betting the color will vary from orange to bright red.