Variation in apparent lunar diameter. These two images show the variation in the apparent diameter of the full Moon, depending on whether it occurs at perigee (closest to the Earth, left), or apogee (farthest from Earth, right). This variation contributes to the phenomenon known as libration. It also accounts for the variation in solar eclipses, from total eclipses to annular eclipses. The labels give the date of the photographs, the apparent angular size (in angular minutes and seconds), and the distance of the Moon from the Earth in kilometres.