An early astronomical almanac by the noted English astronomer
Ephemeris for the Year 1686 is a short astronomical almanac or ephemeris produced by Edmond Halley, the English astronomer best known for his later work on comets. It appeared in the mid-1680s, a period when Halley was actively engaged in astronomical observation and publication, shortly before the appearance of Isaac Newton’s Principia (1687), which Halley famously encouraged and helped bring to press.
The work provides tabulated positions of celestial bodies—chiefly the Sun, Moon, and planets—for the year 1686, calculated for a specific meridian, likely that of London or Greenwich. Such ephemerides were practical tools for navigators, astrologers, and astronomers, enabling them to determine the time, predict eclipses, and locate planets against the fixed stars. The main themes are positional astronomy and the accurate prediction of celestial motions, reflecting the growing emphasis on observational precision in late seventeenth-century science.
Halley’s ephemeris is significant as an example of his early practical contributions to astronomy, demonstrating his skill in computation and his engagement with the broader scientific community of the Royal Society. It also illustrates the state of astronomical practice before the full theoretical synthesis of Newtonian gravitation, when tables were still largely based on empirical corrections to older models. While not as famous as his later work on cometary orbits or his voyage to measure the transit of Venus, this ephemeris represents the kind of routine yet essential astronomical labor that underpinned the scientific advances of the era.
