The largest full moon of 2013, a so-called "supermoon," will light up the night sky this weekend, but there's more to this lunar delight than meets the eye. On Sunday, June 23, at 7 a.m. EDT (1100 GMT), the moon will arrive at perigee — the point in its orbit its orbit bringing it closest to Earth), a distance of 221,824 miles. Now the moon typically reaches perigee once each month (and on some occasions twice), with their respective distances to Earth varying by 3 percent.