The moon exhibited a deep orange glow June 16, 2011, as the Earth cast its shadow in a total lunar eclipse as seen from Manila, Philippines, before dawn. The last total lunar eclipse of the year is Saturday, Dec. 10, 2011. And there won't be another one for three years. Viewers in the western half of the United States will have the best views Saturday well before dawn, Pacific and Mountain Standard Time. (Bullit Marquez/AP)

The eclipse will officially begin at 3:30 a.m. Pacific Standard Time (PST), but not until 4:45 a.m. PST will Earth’s umbral shadow start darkening the moon’s edges. Total eclipse is set to begin at 6:06 a.m., and last for 51 minutes.

Sky watchers in Northern California and the Pacific Northwest will see the fully eclipsed moon emerge from Earth’s shadow just before sunrise. Assuming clear conditions, the eclipsed moon will appear impressively large and low in the sky. Over the Rocky Mountains and northern Plains, the full moon will still be entirely in Earth’s shadow as it sets along the northwestern horizon. Farther east, from the Ohio Valley into the Southern Plains, observers will see the partially eclipsed moon set before it reaches totality.

For western North America, Saturday’s lunar eclipse will offer a rare visual phenomenon in which the rising sun and fully eclipsed moon can be seen at the same time. By definition, a lunar eclipse occurs when the sun and moon are 180 degrees apart, with Earth moving between them to form a straight line. This suggests that observers should be unable to see both the sun and moon during a full lunar eclipse. However, atmospheric refraction – an optical illusion that causes celestial objects to appear higher in the sky than they really are – will allow some locations to see the eclipsed moon and rising sun simultaneously.

East Coast residents disappointed to miss this sky gazing opportunity at least have a partial lunar eclipse to look forward to on June 4, 2012. However, another total lunar eclipse won’t be seen anywhere on Earth until April 15, 2014. For a complete schedule, check out NASA’s lunar eclipse calendar.

Watch this NASA video specially made for the December 10 eclipse:

Those along the East Coast hungry to see the eclipse can watch a webcast at Slooh, the online space camera. Slooh will offer a live feed of the eclipse from telescopes in Australia, Asia and Hawaii which will have some of the best views.

Related from June, 2011: Longest lunar eclipse in eleven years to elude North America

Additional resources:

Upcoming solar and lunar eclipses
Moonrise/set calculator
Sunrise calculator