Man in the Moon Mare Cognitum. This particular human face can also be seen in tropical regions on both sides of the equator. However, the Moon orientation associated with the face is observed less frequently—and eventually not at all—as one moves toward the South Pole. Conventionalized illustrations of the Man in the Moon seen in Western art often show a very simple face in the full moon, or a human profile in the crescent moon, corresponding to no actual markings. "The Man in the Moon" can also refer to a mythological character said to live on or in the Moon, but who is not
Equinox zero. Its latitude will not be exactly zero, since Earth is not exactly in the plane of the ecliptic. Its declination will not be exactly zero either. (The ecliptic is defined by the barycenter of Earth and the Moon combined.) The modern definition of equinox is the instants when the Sun's apparent geocentric longitude is 0° (northward equinox) or 180° (southward equinox). See the adjacent diagram. Because of the precession of the Earth's axis, the position of the vernal point on the celestial sphere changes over time, and the equatorial and the ecliptic coordinate systems change accordingly. Thus when specifying