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TCS Catalogue Format

If you have a long list of objects to observe, you'll probably want to create your own catalogue before the observing run. The telescope operator then doesn't need to type in the coordinates each time you want to move the telescope, which will make observing more efficient.

  • Write your object list in the format:

    NAME ra(hh mm dec(dd mm equinox

    where NAME can have up to 20 characters (no embedded spaces) and equinox specifies the equinox of the source coordinates ("B1950", "J2000" or "APPARENT"). The names and the RA and Dec should not end with a '.', e.g. 'M31.' or '12 58 43.'.

    Note that coordinates in the ICRS system (e.g. those from Gaia) should have their equinox specified as J2000 - do not use the epoch of the catalogue (e.g. 2015.5). The J2000 and ICRS coordinates of an object differ by < 0.1 arcsec.


    M33       01 33 51.02  30 39 36.70   J2000
    NGC157    00 32 14.40 -08 40 20.00   B1950
    GJ398.2   10 39 36.74 +43 06 09.25   APPARENT

    Optionally, proper motions can be added after the column for the equinox. Three numbers should be specified: right ascension proper motion in seconds per year, declination proper motion in arcseconds per year and epoch of coordinates, as in these examples:

    ZEN07    02 43 27.112 +27 42 25.68 J2000.0  0.0006 -0.012 2000.0
    ZEN13    07 53 29.805 +26 45 56.76 J2000.0  -0.0026 0.031 2000.0

    Note the distinction between equinox and epoch. The equinox determines the coordinate system used, usually J2000. The epoch is the date on which the object was at the quoted RA and Dec. Sometimes the epoch is the actual date when the object's position was measured, sometimes it's a prediction for some standard date (e.g. 2000), based on the known proper motion, and a measured position at some other time.

    Other information that can be added to the catalogue entry, following the column for the epoch of proper motion, are parallax (in arcseconds), radial velocity (in km/s) and comments (following a '!', as in this example:

    N00+30 00 08 23.265 +29 05 25.58 J2000 0.01039 -0.1633 2000 .024 -12 ! 2.1 A0
    S00+15 00 13 14.154 +15 11 00.80 J2000 -0.00019 -0.0120 2000 .000 4 ! 2.8 B2

    Please note the following:

    • The entries in the catalog are case insensitive.

    • The target list should include the coordinates of any blind-offset stars.

    • The coordinates should be separated by spaces not colons ':'

    • The file should not include tab, underscore ('_') or non-keyboard characters. Non-keyboard characters often appear in files mailed by mac users. ING support astronomers can filter out characters not compatible with the TCS by running ~crb/wht/cat/filtcat.

    • The TCS default catalogue already includes the ING standards.

    • More information can be found in the TCS manual.

  • Save the file with extension .cat (e.g. Please note that the file name, including extension, must be lower case.

  • Send the catalogue to your support astronomer. He/She will copy onto directory /int/cat mounted on the observing system. For instance, from a portable computer with scp:

    scp 'intguest@intdrpc1:/home/intguest/'

    And then the observer can copy the file /home/intguest/ to /int/cat. If saved using a Mac computer, can be changed to Unix format using:


  • Then the observer can include as an user catalogue on the TCS.

  • Once the observing system is started up, you can point the telescope to any object in the list by typing:

    USER> gocat <NAME>

  • Differential (non-sidereal) tracking rates in right ascension and declination can be entered by issuing the following command on the TCS

    DIFF_RATES <diff_rate_in_ra> <diff_rate_in_dec>

    Right ascension and declination differential tracking rates are in seconds/second and arcseconds/second, respectively, for example:

    DIFF_RATES 0.01 -0.3

This page is maintained by Lilian Dominguez.

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Last modified: 31 December 2023