(from our friends at OMSI in Portland, OR)
Watch the Moon Fade Away
During the morning of December 10, 2011, the Full Moon will slide through the dark shadow of our planet. For 51 minutes, the only light hitting the moon will be the reddish glow from all of Earth’s sunrises and sunsets – a Total Lunar Eclipse!
The moon will be situated in the constellation Taurus and near the most northerly point in the moon’s orbit at that time of the year. The circle is the earth shadow called the umbra.
For the Pacific Northwest viewers, the penumbral eclipse begins at 3:33 a.m. PST and the umbral shadow takes a small, dark bite out of the left edge of the moon starts at 4:45 a.m. PST. For 66 minutes of the partial phase, the darkness engulfs more of the moon’s disk as it slides into the shadow. The partial eclipse ends and totality begins at 6:06 a.m. PST and the point of the greatest eclipse occurs at 6:31 a.m. PST. The eclipse’s total phase will lasts for 51 minutes. The moon will be only 6.5 degrees above the north western horizon at the instant of the greatest eclipse.
What makes it so much fun is that no one can predict what color the moon will turn during totality. Will it be bright orange, or blood red? Only the shadow knows. The total eclipse will end at 6:57 a.m. PST as the moon exits the umbra. Then the moon will set at 7:45 a.m. PST
A lunar eclipse happens when the Moon passes through the Earth’s shadow. Earth always has a shadow, which is created by the Sun. On those rare occasions when the Moon, Earth and the Sun are all lined up just right, the Moon passes through this shadow. This would happen every full moon if the Moon orbited around the Earth in the same plane as the Earth orbits around the Sun. The Moons orbit, however, is tilted about 5 degrees above the Earth-Sun plane. This tilt itself, however, rotates, allowing eclipses to happen when the tilt of this plane lines up with the Earth-Sun plane, blocking sunlight. For future visitors to the moon, the Earth during a total lunar eclipse would appear dark and surrounded by a glowing red ring. Unlike solar eclipses in which the sun’s rays can damage the eyes, lunar eclipses are safe to watch with the naked eye. Binoculars and telescopes will enhance the view. The most important factor will be having clear sky on Saturday morning to view the eclipse!