On Monday, June 4, the full Moon lies directly opposite the Sun in the night sky and skims through the extreme northern tip of the Earth’s shadow. People across much of the Americas, the Pacific Ocean, Australia, and eastern Asia will witness a partial lunar eclipse.

Partial Lunar Eclipse
A partial lunar eclipse on June 15, 2011. The June 4, 2012 eclipse will look about like this at its maximum. Marko Djurica

The first hint of shading at the Moon’s southeastern limb should appear at 10:00 Universal Time (6:00 A.M. EDT, 5:00 A.M. CDT, 4:00 A.M. MDT, and 3:00 A.M. PDT). This is when the Earth’s umbra (Latin for “shadow”) first touches the Moon’s outer limb.

By mideclipse, more than an hour later, at 11:03 Universal Time, 38-percent of the Moon’s disk will be covered by the Earth’s dark umbral shadow. At that time, the Moon will be overhead for observers in the South Pacific, but has already set for the northeastern U.S. and Canada. Only the far western parts of North America, Hawaii and far southern South America will see the dark umbral eclipse from start to finish. Click here for a worldwide map of the partial lunar eclipse.

The partial eclipse will end at 12:07 Universal Time, when the last smudge of the Earth’s umbra will leave the Moon. The next total lunar eclipse, visible for all of North America, will occur the night of April 14-15, 2014.

The eclipse’s most striking effect will be when the dark center of Earth’s shadow makes its way across the southern part of the Moon’s disk. During this interval, the smooth curve of the shadow’s edge on the lunar disk will be a nice reminder to us that the Earth is round.

The portion of the Moon lying outside the umbra, in the shadow’s fringe called the penumbra, will remain quite bright. If you observe with a telescope, try using a magnification of 50X or more and moving the Moon’s bright segment entirely outside the field to get the clearest view of the dim regions inside the umbra.