An (plural: ephemerides ) is a tabulation of the computed positions and velocities of celestial bodies—such as planets, moons, asteroids, and satellites—at specific dates and times. Derived from the Greek word for "diary," it serves as an itinerary for astronomical objects, providing essential data for navigation, scientific research, and astrology. Core Applications

While printed almanacs are still produced for emergency use, most professionals use electronic datasets: Ephemeris - an overview | ScienceDirect Topics

Historically used by mariners to find their way at sea, ephemerides remain a vital backup to modern satellite systems.

Astrologers use these tables to track planetary "transits" (the movement of planets through zodiac signs) and generate birth charts. Scientific and Technical Data

An ephemeris provides more than just a location in the sky. Scientific versions often include:

Missions like Hayabusa2 rely on updated ephemerides of asteroids to achieve high-precision landings (within 100 metres).

Brightness (magnitude), distance from the Sun or Earth, velocity, and apparent diameter.

Calculations have evolved from using Earth’s variable rotation (Universal Time) to highly uniform scales like Ephemeris Time (ET) and its successors, Terrestrial Time (TT) and Barycentric Dynamical Time (TDB), which incorporate relativistic corrections. Leading Sources and Software