An Etymological Dictionary of Astronomy and Astrophysics

The instant when the axis of the Moon’s → shadow cone passes closest to Earth’s center. For → total eclipses, the instant of greatest eclipse is virtually identical to the instants of greatest magnitude and greatest
duration. However, for → annular eclipses, the instant of greatest duration may occur at either the time of greatest eclipse or near the sunrise and sunset points of the eclipse path (F. Espenak, NASA).

See also: Superlative of → great; → eclipse.