Catalogues

User input catalogues are either typed into the TCS (Telescope Control System) computer on line, or loaded via the 1600bpi 9-track tape. A tape in the right format can be prepared and loaded by support staff, given a user catalogue on VMS or Unix. Observation catalogues may be be typed into the telescope computer directly through the user interface or using the OS32 editor. If you have an extensive catalogue this is best done in the afternoon before you start observing. Catalogues can of course be saved to disc, so they are available from night to night, but will normally be deleted at the end of an observing run.

It is possible to select guide stars in advance of an observing run (see Section . on the Guide Star System and Section for allowed positions). Their positions should be entered in the catalogue in the normal way.

A catalogue for the telescope computer is a set of user interface commands, exactly as typed in at a keyboard. The relevant commands are given below. Minimum matching is used, and portions of commands which may be omitted are given in brackets (e.g. the command SOURCE may be shortened to SO). Spaces or semi-colons may be used as separators, the latter being essential if the command is abbreviated (see RA and DECLINATION, below). Anything following an asterisk is treated as a comment and is ignored. The following commands are available:

• SO(URCE) defines a new catalogue entry. The format is SO(URCE name. A source name may have up to 20 alphanumeric characters. Embedded spaces are forbidden.

• R(A) enters the Right Ascension. The format is hours, minutes, seconds. The last two are optional, but the command must be terminated by a semi-colon if they are omitted. Spaces are not required between the hours, minutes and seconds.

• D(ECLINATION) enters a declination. The format is degrees, minutes, seconds. Again, the minutes and seconds may be omitted if the command is terminated by a semi-colon. Spaces are not required between the degrees, minutes and seconds.

• EQ(UINOX). For mean positions, a leading letter indicates the coordinate system:
  B implies mean pre-IAU76 or FK4 (default)
  J implies mean post-IAU76 or FK5 (not yet supported)

  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.

• P(ROPER-MOTION) sets the proper motions. The corresponding epoch is assumed to be the same as the equinox.

• /R(A) proper motion in RA in sec yr

• /D(ECLINATION) proper motion in Declination in arcsec yr.

A catalogue may be in free format. For legibility and neatness, however, it is worth adhering to a more rigid tabular format with one object per line of the file. The format should be as follows:

• The file should consist of 80-byte records. Consequently, no more than 80 characters per line are allowed.

• The filename must consist of up to 8 alphanumeric characters, starting with a letter, and must have the extension .CAT.

• There should be no non-alphanumeric characters (tabs, line feeds, etc.) anywhere in the file.

• A line specifying default parameters and the coordinate type should be given at the beginning of the file, for example:

  .DEFAULT EQUINOX B1950 P/R 0.0 P/D 0.0

  sets the default equinox to 1950 and the default proper motions to zero and specifies mean coordinates. If these parameters are not specified explicitly for objects in the file, then they will take these values.

• The format should be:

  SO OBJECT R hh mm ss.ss D +dd mm ss.s P/R +s.sss P/D +s.sss EQ B yyyy.y

  with the coordinate type, proper motions and equinox omitted if they do not change.