Catalogues

Catalogues of objects may be entered through the user interface of the telescope computer or using an editor on the data-reduction computers. Alternatively, the observer may bring a catalogue on half inch tape, DAT or exabyte cartridge or transfer it via ftp to an account on the cluster, whence it can be accessed by the telescope computer. Catalogues are text files, which can be transferred using any tape format acceptable to a VAX. BACKUP is recommended, with COPY as the second choice. Tape densities of 1600 and 6250 BPI, DATs and exabytes are supported. Those wishing to transfer files from computers other than VAXs or Suns should contact the La Palma computing staff well in advance of their visit.

Catalogues are simply lists of source parameters in free format with spaces separating the fields. All data for an entry should be on one line of the file. Anything following an asterisk is treated as a comment and is ignored. Do not use tab, control or other peculiar characters. The parameters must be in the order: Name, RA, Dec, Equinox, RA proper motion, Dec proper motion, Epoch, Parallax, Radial velocity. The first four parameters are mandatory and the remainder are optional with sensible defaults.

The formats and units of the necessary parameters are as follows:

• Name --- up to 20 characters. Embedded spaces are allowed, but if they are used, then the name must be enclosed in double quotes (e.g. ``NGC 7027'').

• Right ascension --- hours, minutes, seconds, separated by spaces.

• Declination --- degrees, minutes, seconds, separated by spaces.

• Equinox ---

  for mean positions, a leading letter indicates the coordinate system:
  B implies mean pre-IAU76 or FK4
  J implies mean post-IAU76 or FK5

  A number indicates the epoch of the mean equator and equinox of that system (e.g. B1950.0, J1987.5).

  The remaining option is APPARENT (abbreviable to A), for which no number is required or indeed accepted.

The formats, units and defaults of the optional parameters are as follows:

• Proper motions --- in RA (seconds of time per year) and Dec (arcseconds per year). Defaults to zero if not specified.

• Epoch of position --- (year). This should not be confused with the equinox. The epoch of observation is used in conjunction with the proper motions to correct for the space motion of the object. If the epoch is not specified, then it is assumed to be the same as the equinox.

• Parallax --- (arcsec). Generally negligible. Defaults to zero if not specified.

• Radial velocity --- (km s, positive for a receding object). Generally unimportant. Defaults to zero if not specified.

Although not part of a catalogue entry, differential tracking rates may also be specified. These are in seconds of time per second for RA and arcseconds per second for Declination.

Examples of catalogue files are:

1. The simplest possible catalogue, containing name, RA, Dec and equinox:

   3C567 12 34 56.78 -01 23 45.6 B1950
   NGC123 00 12 46.6 05 34 56 J1987.5
   COMET 12 12 12.12 12 12 12.1 A

2. A more complicated entry, including proper motions:

   SP1 00 31 22.2 -12 24 21 B1950.0 0.011 -0.17