|
As Mike points out it happens every year. But big Moon's occur throughout the year at constantly shifting phases. This slow phase shift is due to the approx 2.2 day difference between the Moon's siderial (27.3d) and synodic (29.5) months. The minimum lunar distance beats over the year, maximum less so. So after 6 orbits, the phase shifts by 2.2d x 6 = 13.2 days and occurs close to new moon where it's not nearly as widely covered by the media.
Joe
|