Dec. 19, 2010 -- Barring cloudy weather, astronomy enthusiasts and sky-gazing revelers across North America will be given an early Christmas gift when they will witness a lunar eclipse on Monday night.
A lunar eclipse takes place when the sun, earth and moon are all perfectly aligned with the Earth in the middle. When the moon passes behind the earth, the sun's rays are blocked from striking the moon. This can only occur when the moon is full.
Unlike a solar eclipse, which can only be seen for a few moments from any specific spot, a lunar eclipse can be viewed for several hours.
The eclipse will happen Monday night on the West Coast and during the early hours Tuesday on the East Coast.
According to NASA, although the eclipse is not central, the total phase should last about three and a half hours when it begins as a partial eclipse at 1:33 a.m. ET and it will finish at 5:01 a.m. ET. The totality phase -- when the moon is entirely inside Earth's shadow -- will last a little approximately 72 minutes.
This year's only lunar eclipse actually coincides with the winter solstice, meaning that the moon will appear high in the night sky, aiding visibility for revelers.
There will be two total lunar eclipses in 2011 -- one in June and one in December. North America will miss the June show and witness only a part of next December's eclipse.
Find out more about the Dec. 21 lunar eclipse here at NASA's website.