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495[vsx-dis] UCAC3 identifier format.

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  • Brian D. Warner
    Sep 20, 2009

      Just to tell submitters that the official format for the recently released UCAC3 catalog (see
      3UCAC FFF-NNNNNN instead of UCAC2 NNNNNNNN as in the UCAC2 catalog.

      It will surely be a source of confusion.

      This seems to contradict what is in the UCAC3 README file:

      Official UCAC3 star ID numbers should be utilized for identification purposes and for communication with the UCAC team. The main
      identifier is the running star number in the CCD mean position data (MPOS number) which is provided on the UCAC3 individual star
      records as the last 4-byte integer item. This number spans the range of 3 to 140051297 but includes gaps for stars which did not
      make it into the release. MPOS numbers over 140 million identify high proper motion stars, which have been handled differently in
      the pipeline and were merged at a later stage into the release.

      Alternatively, a unique running star ID number without any gaps can be generated on the fly, counting stars along zones from south
      to north and along RA within each zone, similarly to what was recommended for UCAC2.

      ID = n0 + running star number in zone z

      where z is zone number where the star in question is located (1 to 360; zone 1: -90 to -89.5 decl., ...), n0 is the largest star ID
      number of the previous zone and ID is this official UCAC3 star ID number. A table is provided listing some statistics of zones,
      which include this n0 number.

      If needed, this 9-digit star ID number should be given in connection with the IAU sanctioned acronym of this project and this data
      release number, such as "3UCAC100200300". The star ID number runs from 000000001 to 100766420. Leading zeros are to be used to fill
      9 digits in the star name.

      I find no reference in the README to the 3UCAC NNN-XXXXXXX format. I may have just
      missed it.

      Note also that the largest number given on the SIMBAD page (N=100765502) does not
      agree with the largest number given in the README (N = 100766420).

      You're right: it truly is a source of confusion.

      Clear Skies
      Brian D. Warner
      Palmer Divide Observatory

      Collaborative Asteroid Lightcurve Link
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