Beginning on the West Coast at 7pm, the earth's shadow will bathe the moon in a red or orange tinge.
The last total lunar eclipse until 2010 occurs Wednesday night, with cameo appearances by Saturn and the bright star Regulus on either side of the veiled full moon.
Skywatchers viewing through a telescope will have the added treat of seeing Saturn's handsome rings.
As the moonlight dims — it won't go totally dark — Saturn and Regulus will pop out and sandwich the moon. Regulus is the brightest star in the constellation Leo.
Jack Horkheimer, host of the PBS show "Star Gazer," called the event "the moon, the lord of the rings and heart of the lion eclipse."
Wednesday's event will be the last total lunar eclipse until Dec. 20, 2010. Last year there were two.
The weather could be a spoiler for many in the United States. Cloudy skies are expected for most of the Western states with a chance of snow from the heartland to the East Coast, said Stuart Seto of the National Weather Service.
"It looks like it's going to be a hard one to spot," Seto said.
A total lunar eclipse occurs when the full moon passes into Earth's shadow and is blocked from the sun's rays that normally illuminate it. During an eclipse, the sun, Earth and moon line up, leaving a darkened moon visible to observers on the night side of the planet.
The moon doesn't go black because indirect sunlight still reaches it after passing through the Earth's atmosphere. Since the atmosphere filters out blue light, the indirect light that reaches the moon transforms it into a reddish or orange tinge, depending on how much dust and cloud cover are in the atmosphere at the time.
Wednesday's total eclipse phase will last nearly an hour. Earth's shadow is expected to blot out the moon beginning around 7 p.m. on the West Coast and 10 p.m. on the East Coast. West Coast skygazers will miss the start of the eclipse because it occurs before the moon rises.
Unlike solar eclipses which require protective eyewear, lunar eclipses are safe to view with the naked eye.
Later this year, in August, there will be a total solar eclipse and a partial lunar eclipse.