[vsnet-chat 3616] Re: USNO Ax.0 "identifications"

[Brian Skiff <bas@lowell.edu>]

     Although USNO-Ax.x designations are not assigned in the original data,
the serial numbers generated by ESO/CDS as far as I know are the only ones
actually published.  Also, the Lortet "Dictionary..." makes things pretty
clear:

USNO-A2.0  (US Naval Obs., A2.0 catalogue)
 Write: <<USNO-A2.0 NNNN-NNNNNNNN>>  N=526280881
 Object [*]     (SIMBAD class: Star)
  Note: USNO-A2.0 is based on a re-reduction of the Precision Measuring
        Machine (PMM) scans from POSS-I O and E plates (>=-18deg) and
        SRC-J and ESO-R plates (<=-20deg). U
        The major difference between USNO-A2.0 and its previous version
        USNO-A1.0 is that A1.0 used the Guide Star Catalog as its reference
        frame whereas A2.0 uses the ICRF as realized by the USNO ACT catalog
        (Urban et al. 1997).
        The USNO-A2.0 number is made of a zone number (4 digits from 0000
        to 1725 representing the distance in 0.1deg to the South Pole) and a
        number in the area (8 digits); a dash - must separate the two parts.
         Note that this number differs from the USNO-A1.0 number.
   Ref: =1998USNO2.C......0M
     by MONET D., et al.
        The PMM USNO-A2.0 Catalog. (1998)
        >> A catalogue of astrometric standards.
        ->      <USNO-A2.0 NNNN-NNNNNNNN> N=526280881.
   ==E== Catalogue in electronic form as <I/252>
 Origin of the Acronym: A = Assigned by the author(s)


     _My_opinion_, in general, is to avoid giving USNO-A names at all, simply
because of the confusion already existing, and because these names are
quite transient, and will soon be replaced by USNO-Bx.x, etc.  In publication,
I would suggest noting a very faint star appearing only in that catalogue
with a phrase something like "identifiable with a USNO-A2.0 star located at..."
and not give the number at all.

\Brian

VSNET Home Page

Return to Daisaku Nogami

---

vsnet-adm@kusastro.kyoto-u.ac.jp