Ephemeris — Definition

An ephemeris is the working dictionary of an astrologer. Before software, ephemerides were thick books listing the daily longitude of each planet; today they are usually queried by computer. They allow astrologers to look up where any planet was on any date — essential for casting natal charts, tracking transits, and timing events. The plural is ephemerides.

Origin

From Greek ephemeros, "lasting only a day." A daybook of the heavens.

Example

Without a birth time, an ephemeris can still tell you the Sun, Moon, and most planet positions to within a degree.