The historic transit of Venus across the sun Tuesday is a must-see for skywatchers, but observers shouldn't overlook another celestial event that comes just one day earlier - a partial lunar eclipse of the June full moon.
On Tuesday, Venus will trek across the sun's face from Earth's perspective, marking the last such transit of Venus until 2117. In a sort of celestial warmup, the full moon will dive through Earth's shadow on Monday morning to produce a partial lunar eclipse that will be visible to observers throughout parts of North America, Asia and the Pacific region, weather permitting.
The lunar eclipse comes two weeks after the May 20 annular solar eclipse that enthralled skywatchers around the world, and that's no accident.
Solar eclipses are always accompanied by lunar eclipses, either two weeks before or two weeks after. The moon travels halfway in its orbit around Earth in that time, forming another straight line with our planet and the sun. (In solar eclipses, the moon blots out the sun, while lunar eclipses occur when Earth's shadow covers all or part of the moon.)
The same parts of the world that were treated to the May 20 "ring of fire" solar eclipse will thus be favorably placed for Monday's partial lunar eclipse. Much of central and western North America should get a good show, as should eastern Asia, Australia and the Pacific region. The full moon of June is known as the Strawberry Moon because it occurs during the short strawberry-harvesting season this month.