Ephemeris

Definition

A table (modern: a database or software output) giving the positions of the Sun, Moon, planets, and other celestial bodies — typically by longitude, latitude, declination, and motion — for successive dates and times. In Late-Babylonian mathematical astronomy the term denotes a particular text-genre: a tabular cuneiform output of mathematical procedures, organised in numbered columns and computing dates and longitudes of lunar and planetary synodic phenomena. In modern Western practice an ephemeris is any reference table or database the astrologer queries to find planetary positions for a chart.

In Tradition

Across Babylonian, Greek, Arabic, and modern Western astronomy and astrology, the ephemeris is the working instrument that turns observation and theory into chart data. Whether the source is a Late-Babylonian cuneiform tablet, Ptolemy's procedural Almagest, a printed 20th-century ephemeris, or the Swiss Ephemeris programmatic library, the function is the same: supply the positions a practitioner needs to cast a chart for a given date and place.

In Practice

When casting a chart, the astrologer queries an ephemeris for the longitude (and often latitude, declination, and motion) of each body at the moment of birth. Modern practice has shifted from printed annual ephemerides (Raphael's, the Rosicrucian, the American Ephemeris) to programmatic libraries — the Swiss Ephemeris and JPL DE-series — embedded in chart software. Older practitioners still consult printed ephemerides for transit planning, manual calculation, and historical research. In Hellenistic-revival work, the historical Babylonian and Greek ephemeris texts also matter as sources for technique and source-history.

Historical Origin

The Late-Babylonian mathematical-astronomy corpus (Hunger & Pingree, Astral Sciences in Mesopotamia §C.2.4-2.5; Rochberg, The Heavenly Writing Ch. 4) preserves the earliest ephemeris-genre tablets — System A and System B lunar and planetary tables, often with the Akkadian title tersītu in their colophons. Hunger and Pingree estimate computational capacity for all five planets was in place by mid-3rd c. BCE. The genre passes through Ptolemy's Almagest tables into the Arabic-Latin reception (Toledan, Alfonsine) and into modern printed and programmatic ephemerides.

Etymology

Origin: Greek. Meaning: Daily, for a day.

Further Reading

• Francesca Rochberg, The Heavenly Writing
• Hermann Hunger & David Pingree, Astral Sciences in Mesopotamia
• Otto Neugebauer, A History of Ancient Mathematical Astronomy