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MJD -- column label: MJD_OBS

Occasionally, one finds an ephemeris given with Julian Dates as argument. Only the Modified Julian Date is used here. This must be a double-precision (R*8) variable, in F12.5 format. Modified Julian Dates are discussed further in section I.6 on data files.

The object name must be repeated on successive rows of an ephemeris file that refer to the same object; the repeated name tells programs to look for ephemeris data, and to interpolate positions as required. One table file can contain several objects, which may be convenient for some observing programs.

If the tabular positions are referred to the equator and equinox of date, as in some of the tables in the Astronomical Almanac, the EQUINOX column can be omitted. If astrometric positions are given, as in Ephemerides of Minor Planets, the EQUINOX column is required. In general, ephemeris data for moving objects should be kept in table files separate from star-position files.

Petra Nass