Skywatchers across western North America have set alarms to wake before dawn to see a rare Super Blue Blood Moon, with hundreds expected to view the phenomenon from a Los Angeles mountaintop.
As is the case with all total lunar eclipses, the Earth will cast a darkened red-tinted shadow across the face of its natural satellite, hence the term "blood moon" but two other factors are combining to make Wednesday's spectacle particularly unusual.
The eclipse will unfold during the rare occasion of a second full moon in a single month, otherwise known as a "blue moon", and during a point in the moon's orbit at which it has reached its closest position to Earth, thus making it appear larger and brighter in the sky than normal as a "super moon".
The reddish appearance of the lunar surface - the moon's image does not vanish entirely during the eclipse - is due to rays of sunlight passing through Earth's atmosphere as the moon falls into our planet's shadow.
The last time all three conditions occurred for a single lunar eclipse visible from North America was in 1866, according to the meteorological forecaster AccuWeather.
In Los Angeles, a crowd ranging from 1000 to 2000 people is expected to make a pilgrimage in the dark to the Griffith Observatory on Mount Hollywood, where extra telescopes will be set up for them to see the celestial show, Griffith Observatory officials say.
"Griffith Observatory is all about having an eyeball to the sky and so it's one thing to learn about this event in a book but it's another to see it for yourself," observatory director Ed Krupp said.
