Because precession is a large effect, we must know the equinox to which these coordinates refer. Although this is usually a constant for a whole table, and so might be stored in a descriptor, observers may want to use lists of program stars compiled from heterogeneous sources. Therefore, the year of the equinox must be stored in a separate column of Real*4 values, with the label EQUINOX. This column is easily created for a star catalog with a single equinox date using the COMPUTE/TABLE tablename :EQUINOX = year command. A format of F7.2 is satisfactory.
Table: Columns for star-catalog table files