Orbits of Earth and Moon. Looking at a two-dimensional diagram, you might wonder why there isn't an eclipse every month. The answer is that the Moon's orbit is slightly tilted with respect to the Earth's orbit. The two points where its orbit crosses Earth orbit are called nodes. Only if the Moon is full when it's near a node do the Sun, Earth and Moon line up for a lunar eclipse. ©Mona Evans, “Lunar Eclipses” http://www.bellaonline.com/articles/art28454.asp

Total lunar eclipse for the Americas on night of April 14-15 | Tonight | EarthSky

Total lunar eclipse for the Americas on night of April 14-15 | Tonight | EarthSky

Total lunar eclipse for the Americas on night of April 14-15 | Tonight | EarthSky

Total lunar eclipse for the Americas on night of April 14-15 | Tonight | EarthSky

The Moon

Moon | Sun

Moon

Moon

Sun eclipsed by Earth (left) and Moon (right). (Image credit: NASA/SDO) The Solar Dynamics Observatory orbits Earth in such a way that very occasionally it lines up with Earth & Sun (or Moon & Sun) to cause an eclipse. The Moon's shadow is better-defined & more curved than Earth's, because the Moon has no atmosphere, and is smaller and farther away from the Satellite. ©Mona Evans, “Lunar Eclipses” http://www.bellaonline.com/articles/art28454.asp

moon texture

The Mineral Moon (NASA/JPL)

Solar Eclipses: An Observer's Guide (Infographic) - When the moon covers up the sun, skywatchers delight in the opportunity to see a rare spectacle. Mona Evans, “Solar Eclipses” http://www.bellaonline.com/articles/art28395.asp

Moon obscuring the Sun, with Venus on top

If you were on the Moon during a total lunar eclipse, you'd see a total solar eclipse. It might look something like this, with the Earth's nightside faintly shining. (Credit: Hana Gartstein) Mona Evans, "Lunar Eclipses" http://www.bellaonline.com/articles/art28454.asp

International Space Station silhouetted against the moon

Partial lunar eclipse from Hudson, Florida. June 4, 2012. (Photo: David Dickinson) I love the way he's caught the eclipsed Moon near the horizon through the trees. ©Mona Evans, “Lunar Eclipses” http://www.bellaonline.com/articles/art28454.asp

Lunar Eclipse infographic. (Credit: Karl Tate) Mona Evans, “Lunar Eclipses” http://www.bellaonline.com/articles/art28454.asp

Total lunar eclipse. The green light beam is a laser being used to measure the Earth-Moon distance. The laser's target is a retroreflector left on the Moon by Apollo 15 astronauts. Timing the return of the laser pulse allows a highly accurate determination of the distance traveled. Performance is improved during the eclipse because direct sunlight is blocked. (Credit & copyright: Dan Long) Mona Evans, "Blood Moons and Lunar Tetrads" http://www.bellaonline.com/articles/art301030.asp

Total Eclipse By Pazav70

A total lunar eclipse occurs during a Full Moon when the Sun, Earth and Moon line up exactly in that order. Light from the Sun (white lines) skirts the Earth’s atmosphere, which bends and reddens it. It reaches and reflects off the Moon back toward the Earth and we see a beautifully colored disk during totality. Credit: NASA with additions by Bob King.