A tabulation of the locations and related data for a celestial body for given epochs (dates) at uniform intervals of time. In particular, a publication containing such data for a number of celestial bodies. The Astronomical Ephemeris (formerly the American Ephemeris and Nautical Almanac) is such a publication. It contains, for specified instants, the coordinates of the principal celestial bodies; the constants specifying the position of the coordinate system used; numbers used in calculating the effects of changes in the location of the observer; and, in general, data on all those phenomena relating to celestial bodies which may be regarded as functions of time and which are of interest to navigation and related arts. The plural of ephemeris is ephemerides. While custom has approved the use of the singular form to designate the publication as a whole, the plural form is used when tabulations for specific bodies are discussed e.g., the ephemerides of Mercury and Venus. When tabulation for one specific body is discussed, the singular form is used e.g., the ephemeris of Mercury.