Lunar Cycles • A visual guide
Perigee and Apogee
The Moon’s changing distance from Earth
The Moon’s distance changes along its orbit. Perigee names the closest point; apogee names the farthest.
Scroll the diagram sideways to explore its labels.
Two turning points in distance
The Moon’s orbit is slightly elliptical. Perigee and apogee mark its nearest and farthest distances from Earth. Those distances vary from one orbit to another, so neither term represents one permanently fixed distance.
Distance and apparent size
A closer Moon appears a little larger in the sky; a farther Moon appears a little smaller. The Moon itself has not changed size. A full moon near perigee is often called a supermoon, an informal term rather than an official astronomical classification.
A different cycle from phase
The interval from one perigee to the next is called the anomalistic month. The phase cycle is the synodic month. These cycles have different lengths, so perigee does not always coincide with full moon. Distance and phase describe different aspects of the same moving Moon.
Source: Fred Espenak, NASA GSFC — Eclipses and the Moon’s Orbit