Lunar Eclipses take place only during a full moon, but they do not occur every full moon. This is because the path of the moon around the Earth varies about 6 degrees from the path of the Earth around the sun. Because of this difference, the moon frequently passes either above or below the Earth’s shadow, and escapes being eclipsed. A total lunar eclipse may last an hour and 40 minutes. The greatest number of lunar eclipses that can occur in one year is three.
Actually, the moon may not completely disappear from sight during a total eclipse. Sometimes it becomes copper colored, because the sun’s light strikes the atmosphere and refracts into the shadow of the Earth that covers the moon. If the atmosphere near the Earth is exceptionally cloudy, it may absorb the light rays, and the moon will disappear completely from sight.