But there's more! The August 30th blue moon is also a supermoon. The moon's orbit isn't a perfect circle, so sometimes it's a little farther away from Earth and sometimes closer. At its closest point, called perigee, it's 14% closer than at its farthest. About 3 to 4 times a year, the full moon phase happens to coincide with the Moon reaching perigee, and we call that event a supermoon. While it technically appears a little bit bigger (and a tad brighter) than the average full moon, the difference is not super noticeable to the eye.