LOS ANGELES: The longest partial lunar eclipse in nearly 600 years, which will bathe the Moon in red, was visible for a big slice of humanity on Friday.

The celestial show will see the lunar disc almost completely cast in shadow as it moves behind the Earth, reddening 99 percent of its face.

The spectacle was visible for all of North America and parts of South America from 0602 GMT Friday, and may later be seen in Polynesia, Australia and northeast Asia.

By 0750 GMT, sky-watchers with a cloud-free view in those regions saw the Moon half covered by the Earth’s penumbra — the outer shadow.

Space scientists said Thursday that by 0845 GMT the Moon would appear red, with the most vivid coloring visible at peak eclipse 18 minutes later.

The dramatic red is caused by a phenomenon known as “Rayleigh scattering”, where the shorter blue lightwaves from the Sun are dispersed by particles in the Earth’s atmosphere.

Red lightwaves, which are longer, pass easily through these particles.

“The more dust or clouds in Earth’s atmosphere during the eclipse, the redder the Moon will appear,” a NASA website explained.