A FITS-format binary table containing at least two columns, which are assumed to contain RA and Dec values for the sources. These may have either real32 or real64 data types (their data types need not be the same). The names of these columns are not constrained but if they are not called RA and DEC then their names should be supplied to the parameters racolumn and deccolumn. Units can be either decimal degrees (radecunits=`decimaldeg') or radians (radecunits=`radians'). String-type columns with HH:MM:SS-style data may be accepted by a future version of the task.
Additional columns as listed in parameters expression, ncutsortexpression, radiusexpression, sortexpression, labelexpression and extragaiacolumns may be required.
