Light seems to pool at the bottom of the full moon in a picture of a lunar eclipse taken from Iran in 2008.
This weekend sky-watchers in western North America will be able to catch a similar sight during the last total lunar eclipse until 2014. The moon show will be visible from the Pacific coast on Saturday at dawn, appearing low in the western horizon.
The entire lunar eclipse will be visible from East Asia, Australia, and the far western part of North America, including Alaska as well as Canada's Yukon and Northwest Territories.
The eclipse will last for three and a half hours, starting at 4:45 a.m. Pacific time.
A composite picture shows the stages of an August 2007 lunar eclipse before, during, and after totality-when the full moon is completely blocked from direct sunlight. Totality for the December 10, 2011, lunar eclipse will start at 6:05 a.m. PT and last until 6:57 a.m. PT. (See pictures from the previous total lunar eclipse in June.)
Rather than going completely dark, the moon takes on a deep reddish hue during a total lunar eclipse.
"As the entire moon passes through the Earth's shadow cast by the sun in space, sunlight scattering off our planet's dusty atmosphere and subsequently reflecting off the surface of the moon will make it appear to change color," said Raminder Singh Samra, an astronomer at the H.R. MacMillan Space Centre in Vancouver, Canada.
Expect to see the lunar disk go from dark gray during the partial phase to reddish orange during totality, he said.
A composite picture shows the stages of a total lunar eclipse in July 2000, seen as the moon sets over Hawaii.
Lunar eclipses can occur only when the full moon, Earth, and the sun are aligned so that the moon crosses through Earth's shadow. (Watch a moon facts video.)
Due to the moon's tilted orbit around Earth, lunar eclipses happen only a few times a year, Samra said. The eclipse can be full or partial, depending on how much of the lunar disk falls in our planet's shadow.
Red bugloss plants, native to Tenerife in the Spanish Canary Islands, point like fingers at a lunar eclipse as it progresses across the sky in May 2003. The composite picture was taken on Teide, a dormant volcano.