The total eclipse is the second of four over a two-year period that began April 15 and concludes on Sept. 28, 2015. The so-called tetrad is unusual because the full eclipses are visible in all or parts of the United States, according to retired NASA astrophysicist Fred Espenak.
Weather permitting, Wednesday's eclipse should be visible to skywatchers in North America, Australia, western South America and parts of East Asia. The eclipse should reach totality just before sunrise, at 6:25 a.m. EDT (1025 GMT).
If cloudy skies are a problem, both NASA.gov and Slooh.com will be hosting live webcasts. NASA's begins at 3 a.m. EDT and Slooh's at 5 a.m. EDT.
An eclipse occurs when the moon passes through Earth's shadow, called the umbra.
As for the reddish hue, Tony Phillips, an astronomer with SpaceWeather.com, says to imagine yourself on the moon: "Overhead hangs Earth, nightside down, completely hiding the sun behind it. The eclipse is under way. You might expect Earth to be utterly dark, but ... the rim of the planet is on fire."
"You're seeing every sunrise and every sunset in the world, all at once," Phillips wrote in an article on NASA's science website.
The light beams into Earth's shadow, filling it with a coppery glow that colors the moon red, he said.
The entire eclipse will be visible from the Pacific Ocean, regions immediately bordering it and the northwestern section of North America. Farther east, the later phases of the eclipse occur after moonset. The eclipse will not be visible from Europe, Africa and the Middle East, NASA said.