greatest eclipse – For solar eclipses, Greatest Eclipse (GE) is defined as the instant when the axis of the Moon’s shadow cone passes closest to Earth’s center. The computation of the duration of the total (or annular) phase at this point is typically done using a smooth edge for the Moon that ignores the effects of mountains and valleys along the lunar limb. For total eclipses, the instant of Greatest Eclipse offers a good approximation (typically ~1-2 seconds) to the Greatest Duration of totality along the entire eclipse path. The instant of Greatest Eclipse is easily calculated for total, annular and partial eclipses, and is the standard time used for comparing different eclipses with each other.
For annular eclipses, the instant of Greatest Duration may occur either near the time of Greatest Eclipse or near the sunrise and sunset points of the eclipse path.
For lunar eclipses, Greatest Eclipse is defined as the instant when the Moon passes closest to the axis of Earth’s shadow.