Tables of total solar and lunar eclipses are listed in Appendices I and II, respectively.
An eclipse of the Sun or Moon occurs whenever Earth passes directly between the Sun and the Moon or the Moon passes directly between the Earth and the Sun. In the former case, the Earth casts a broad shadow onto the Moon, creating a lunar eclipse, and in the latter case, the Moon casts its tiny shadow on the Earth, creating a solar eclipse.
Most of the time, orbital geometry prevents these bodies from being in perfect alignment because, rather than lying exactly within the plane of the solar system (i.e., the ecliptic), the plane of the Moon's orbit is inclined 5.1° with respect to the ecliptic. Generally, when the Sun, Moon, and Earth are in a row, the Moon is slightly out of line, being either above or below the ecliptic plane. Thus, the new Moon passes a little above or below the Sun, while the full Moon passes slightly above or below Earth's shadow. This 5.1° inclination prevents us from seeing total lunar and solar eclipses every month.
The Moon's orbital plane and the ecliptic intersect, however, at two crossover points called 'nodes.' A solar eclipse can only occur when the Moon and Sun are at or near the same node; and a lunar eclipse can only occur when the Sun and Moon lie at opposite nodes. The point in the lunar orbit where the Moon moves southward through the ecliptic plane (with respect to Earth's north-south axis) is called the descending node; the point where it moves northward is called the ascending node. Either node will suffice for an eclipse.
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