Moving objects

For moving objects such as asteroids, comets, or planets, it is useful to include ephemeris information, both to provide predicted coordinates for planning observations, and to allow accurate airmass calculations in the reductions. Each such object requires several positions, each associated with a time. These times can be given either as Modified Julian Dates ( MJD = JD - 2400000.5), or as ordinary date strings like 1995 Jan 23.0. To allow good interpolation, include two ephemeris entries before and two after the interval of observations. The tabular interval need not be one day, but can have any constant value from one table entry to the next.