Definition of ephemeris in US English:



Astrology Astronomy
  • 1A table or data file giving the calculated positions of a celestial object at regular intervals throughout a period.

    • ‘Global networks of tracking stations produce the observations that make generation of the precise ephemerides possible.’
    • ‘It's not commonly realised that there is a strong notional element in some of the times so confidently listed in the ephemeris, as will become clear if you compare the times given for aspects of the major planets in different ephemerides.’
    • ‘The navigation message contains the satellite ephemeris, which is a numerical model of the satellite's orbit.’
    • ‘The GPS position solution can be improved by using a better satellite ephemeris.’
    • ‘Timing an occultation to a fraction of a second allows the observed location to be referenced against the predicted position from the computed ephemeris, perhaps leading to an update.’
    1. 1.1 A book or set of such tables or files.
      • ‘He purchased an ephemeris.’
      • ‘The first of his long-running annual ephemerides appeared in 1655 and the following year he published An Emendation of Hartgil's Astronomical Tables.’
      • ‘Alternatively, you can use an ephemeris to look up the daily positions, but these are usually more expensive and not really worth buying unless you are going to be tracking other astrological things too.’


Early 16th century: from Latin, from Greek ephēmeros ‘lasting only a day’.