ACDS V10.0 - Tue Aug 10 21:31:39 CEST 2021
|  | Detailed Description of I/322A :
 UCAC4 Catalogue (Zacharias+, 2012)
 |  | 
Note : this is the description file of the original catalog.
This HTML page corresponds well to the original description, but some minor
changes in the format may have been introduced in the FITS output
files in order to allow for arithmetic operations on quantities
such as coordinates and times. h:m:s and d:m:s units are normally
converted into degrees, and YYYY-MM-DD into julian days.
Similarly, some slight changes may have been introduced in the
units; the value given in the HTML files supersedes the value indicated in the ReadMe
file for this catalogue.
I/322A              UCAC4 Catalogue                 (Zacharias+, 2012)
================================================================================
The fourth U.S. Naval Observatory CCD Astrograph Catalog (UCAC4)
     Zacharias N., Finch C.T., Girard T.M., Henden A., Bartlett J.L.,
     Monet D.G., Zacharias M.I.
    <Astron. J. 145, 44 (2013)>
    =2012yCat.1322....0Z
    =2013AJ....145...44Z
================================================================================
ADC_Keywords: Surveys ; Positional data ; Proper motions
Description:
    UCAC4 is a compiled, all-sky star catalog covering mainly the 8 to 16
    magnitude range in a single bandpass between V and R. Positional
    errors are about 15 to 20 mas for stars in the 10 to 14 mag range.
    Proper motions have been derived for most of the about 113 million
    stars utilizing about 140 other star catalogs with significant epoch
    difference to the UCAC CCD observations. These data are supplemented
    by 2MASS photometric data for about 110 million stars and 5-band
    (B,V,g,r,i) photometry from the APASS (AAVSO Photometric All-Sky
    Survey) for over 50 million stars. UCAC4 also contains error estimates
    and various flags. All bright stars not observed with the astrograph
    have been added to UCAC4 from a set of Hipparcos and Tycho-2 stars.
    Thus UCAC4 should be complete from the brightest stars to about R=16,
    with the source of data indicated in flags. UCAC4 also provides a link
    to the original Hipparcos star number with additional data such as
    parallax found on a separate data file included in this release.
    The proper motions of bright stars are based on about 140 catalogs,
    including Hipparcos and Tycho, as well as all catalogs used for the
    Tycho-2 proper motion construction. Proper motions of faint stars are
    based on re-reductions of early epoch SPM data (-90 to about -20 deg
    Dec) and NPM (PMM scans of early epoch blue plates) for the remainder
    of the sky. These early epoch SPM data have also been combined with
    late epoch SPM data to arrive at proper motions partly independent
    from UCAC4 (Girard et al. 2011AJ....142...15G, Cat. I/320). The NPM
    data used in UCAC4 are not published. No Schmidt plate data are used
    in UCAC4.
    The unpublished plate measure data obtained by StarScan from the AGK2,
    the Hamburg Zone Astrograph, the USNO Black Birch Astrograph, and the
    Lick Astrograph have contributed to considerable improvement in proper
    motions for stars mainly in the 10 to 14 mag range (down to the UCAC
    limit for Lick data); however, these data do not cover all sky.
    Recources permitting, USNO plans to release the individual CCD
    observations (RA,Dec at epoch of each CCD observations) in the future.
    Please contact nz@usno.navy.mil if you are interested in obtaining
    this set of about 50 GB data. We will likely request that interested
    users provide an external disk drive for the data release.
Acknowledging UCAC4:
    The paper (Zacharias et al., 2013, AJ, 145, 44) should be cited
    whenever UCAC4 data is utilized.
File Summary:
       FileName      Lrecl  Records   Explanations
×                   80        .   This file
× ReadMe            80        .   This file
× out.sam          294     1000   Sample UCAC4 output (out of 113780093 stars)
× ucac4doc.txt      79     2008   Description of UCAC4 (readme_u4)
See also:
  http://www.usno.navy.mil/USNO/astrometry/optical-IR-prod/ucac : UCAC home page
   I/289 : UCAC2 Catalogue (Zacharias+ 2004)
   I/315 : UCAC3 Catalogue (Zacharias+ 2009)
   I/247 : The AC2000 Catalogue (Urban+ 1997)
   I/259 : The Tycho-2 Catalogue (Hog+ 2000)
   I/264 : Sixth Catalogue of Fundamental Stars (FK6) (Wielen+ 2000)
   I/277 : SPM Catalog 2.0 (Platais+ 1998)
   I/317 : The PPMXL Catalog (Roeser+ 2010)
  II/246 : 2MASS All-Sky Catalog of Point Sources (Cutri+ 2003)
 VII/233 : The 2MASS Extended sources (IPAC/UMass, 2003-2006)
 VII/242 : LEDA galaxies with DENIS measurements catalog (Paturel+, 2005)
 VII/248 : Quasars and Active Galactic Nuclei (12th Ed.) (Veron+ 2006)
Byte-by-byte Description of file:  out.sam
   Bytes Format Units   Label    Explanations
   1- 10  A10   ---     UCAC4    UCAC4 recommended identifier (ZZZ-NNNNNN) (1)
  12- 22  F11.7 deg     RAdeg    Mean right ascension (ICRS), Ep=J2000 (2)
  23- 33  F11.7 deg     DEdeg    Mean declination (ICRS), Ep=J2000 (2)
  35- 37  I3    mas     e_RAdeg  Mean error of RAdeg at mean epoch
  39- 41  I3    mas     e_DEdeg  Mean error of DEdeg at mean epoch
  43- 46  I4    mas     ePos     Total mean error on position at Ep=J2000 (3)
  48- 54  F7.2  yr      EpRA     Central epoch for mean RA
  56- 62  F7.2  yr      EpDE     Central epoch for mean Declination
  64- 69  F6.3  mag     f.mag    ? UCAC fit model magnitude (579-642nm) (4)
  71- 76  F6.3  mag     a.mag    ? UCAC aperture magnitude (579-642nm) (4)
  78- 81  F4.2  mag     e_a.mag  ? Mean error on f.mag and a.mag (5)
      85  I1    ---     of       [0/9] UCAC4 object classification flag (6)
  87- 88  I2    ---     db       [0/36] UCAC4 double star flag (7)
  90- 92  I3    ---     Na       [0/71] Number of UCAC observations for the star
  94- 96  I3    ---     Nu       [0/70] Number of used UCAC observations (8)
  98-100  I3    ---     Nc       [1/38] Number of catalog positions used for pm
 102-109  F8.1  mas/yr  pmRA     ? Proper motion in RA(*cos(Dec)) (9)
 111-118  F8.1  mas/yr  pmDE     ? Proper motion in Dec (9)
 120-123  F4.1  mas/yr  e_pmRA   ? Mean error on pmRA (9)
 125-128  F4.1  mas/yr  e_pmDE   ? Mean error on pmDE (9)
--------------------------------------------------------------------------------
 130-138  I9    ---     MPOS1    [1/182895114] Unique star ID number (10)
 140-149  A10   ---     UCAC2    UCAC2 (Cat. I/289) designation (ZZZ-NNNNNN)
 151-162  A12   ---     Tycho-2  Tycho-2 (Cat. I/259) designation (FFFF-NNNNN-N)
--------------------------------------------------------------------------------
 164-173  I10   ---     2Mkey    ? 2MASS (Cat. II/246) Unique source identifier
 175-180  F6.3  mag     Jmag     ? 2MASS J magnitude (1.2um)
 182-185  F4.2  mag     e_Jmag   ? Mean error (rounded to 0.01mag)
     186  A1    ---     ---      [:]
 187-188  I02   ---     q_Jmag   [0,58]? J-band quality-confusion flag (11)
 190-195  F6.3  mag     Hmag     ? 2MASS H magnitude (1.6um)
 197-200  F4.2  mag     e_Hmag   ? Mean error (rounded to 0.01mag)
     201  A1    ---     ---      [:]
 202-203  I02   ---     q_Hmag   [0,58]? H-band quality-confusion flag (11)
 205-210  F6.3  mag     Kmag     ? 2MASS Ks magnitude (2.2um)
 212-215  F4.2  mag     e_Kmag   ? Mean error (rounded to 0.01mag)
     216  A1    ---     ---      [:]
 217-218  I02   ---     q_Kmag   [0,58]? K-band quality-confusion flag (11)
--------------------------------------------------------------------------------
 220-225  F6.3  mag     Bmag     ? B magnitude from APASS (12)
     226  A1    ---     ---      [:]
     227  A1    ---     f_Bmag   [.-] Actual or S/N estimated error (12)
 228-229  I02   cmag    e_Bmag   ? Estimated error on Bmag (12)
 231-236  F6.3  mag     Vmag     ? V magnitude from APASS (12)
     237  A1    ---     ---      [:]
     238  A1    ---     f_Vmag   [.-] Actual or S/N estimated error (12)
 239-240  I02   cmag    e_Vmag   ? Estimated error on Vmag (12)
 242-247  F6.3  mag     gmag     ? g magnitude from APASS (12)
     248  A1    ---     ---      [:]
     249  A1    ---     f_gmag   [.-] Actual or S/N estimated error (12)
 250-251  I02   cmag    e_gmag   ? Estimated error on gmag (12)
 253-258  F6.3  mag     rmag     ? r magnitude from APASS (12)
     259  A1    ---     ---      [:]
     260  A1    ---     f_rmag   [.-] Actual or S/N estimated error (12)
 261-262  I02   cmag    e_rmag   ? Estimated error on rmag (12)
 264-269  F6.3  mag     imag     ? i magnitude from APASS (12)
     270  A1    ---     ---      [:]
     271  A1    ---     f_imag   [.-] Actual or S/N estimated error (12)
 272-273  I02   cmag    e_imag   ? Estimated error on imag (12)
--------------------------------------------------------------------------------
     275  I1    ---     g        [0,3] g-flag from SPM (13)
     276  I1    ---     c        [0,7] c-flag from SPM (14)
     277  A1    ---     ---      [.]
     278  I1    ---     H        [0/9] Hipparcos/Tycho flag (15)
     279  I1    ---     A        [0/8] AC2000 flag (16)
     280  I1    ---     b        [0/8] AGK2 Bonn match flag (16)
     281  I1    ---     h        [0/8] AGK2 Hamburg match flag (16)
     282  I1    ---     Z        [0/8] Zone astrographic match flag (16)
     283  I1    ---     B        [0/8] Black Birch match flag (16)
     284  I1    ---     L        [0/8] Lick Astrographic match flag (16)
     285  I1    ---     N        [0/8] NPM Lick match flag (16)
     286  I1    ---     S        [0/8] SPM Lick match flag (16)
 289-290  I2  [6arcsec] LEDA     LEDA I-band galaxy match (17)
 293-294  I2    arcsec  2MX      2MASX K-band match (18)
Note (1): the UCAC4 number is the recommended identification of UCAC4 stars.
     It made as "ZZZ-NNNNNNN", where zzz is the zone number (between 1 and
     900 from South pole to North pole, each zone being 0.2° wide), and
     nnnnnn the 6-digit running number in the zone.
Note (2): Positions are on the International Celestial Reference System
     (ICRS) as represented by the Hipparcos / Tycho-2  catalogs. The epoch
     for the positions of all stars is J2000.0: the weighted mean catalog
     position was updated using the proper motions. The observational UCAC
     position is but one of several going into these values and is not
     given in the UCAC4; thus the original UCAC observation cannot be
     recovered from these data.
Note (3): taking into account the propagation of the proper motion error
     between the mean epoch and J2000.
Note (4): systematic errors are expected to be below 0.1mag. The aperture
     photometry (a.mag) is considered more robust, particularly for "odd"
     cases, while the model fit magnitude is expected to be more accurate
     for "well behaved" stars.
Note (5): For many stars a photometric error based on the scatter from
     individual observations of that star on different CCD frames could be
     obtained.  A model error was also attempted to be assigned, based on
     the S/N ratio.  The error quoted here is the larger of the 2.  If that
     error exceeds 0.9mag the error was set to 0.9mag
Note (6): the object type flag is used to identify possible problems
    with a star and has the following meaning:
    0 = good, clean star, no known problem
    1 = near overexposed star
    2 = possible streak object
    3 = high proper motion (HPM) star
    4 = actually use external HPM data instead of UCAC4 observed data
        (accuracy of positions varies between catalogs)
    5 = poor proper motion solution, report only CCD epoch position
    6 = substitute poor astrometric results by FK6/Hip/Tycho-2 data
    7 = added supplement star (no CCD data) from FK6/Hip/Tycho-2 data,
        and 2 stars added from high proper motion surveys
    8 = high proper motion solution in UCAC4, star not matched with PPMXL
    9 = high proper motion solution in UCAC4, discrepant motion to PPMXL
Note (7): The double star flag is used to indicate the type/quality
     of double star fit. It is a combination of 2 flags, dsf+dst:
  * dsf = double star flag, represents the overall classification:
      0 = single star
     10 = component #1 of "good" double star
     20 = component #2 of "good" double star
     30 = blended image
  * dst = double star type, derived from pixel data image profile fits
          (largest value of all images used for this star):
      0 = no double star, not sufficient #pixels or elongation
          to even call double star fit subroutine
      1 = elongated image but no more than 1 peak detected
      2 = 2 separate peaks detected -> try double star fit
      3 = secondary peak found on each side of primary
      4 = case 1 after successful double fit (small separation, blended image)
      5 = case 2 after successful double fit (most likely real double)
      6 = case 3 after successful double fit (brighter secondary picked)
Note (8): A zero for the number of used images indicates that all images
     have some "problem" (such as overexposure). In that case an unweighted
     mean over all available images (Na) is taken to derive the mean
     position, while normally a weighted mean was calculated based on the
     "good" images, excluding possible problem images (Nu<=Na).
Note (9):  For astrometric data copied from the FK6, Hipparcos and Tycho-2
     catalogs a mean error in positions was adopted depending on input
     catalog and the brightness of the star rather than giving the
     individual star's error quoted in those catalogs.
Note (10):  This unique star identification number is between 200001 and
     321640 for Hipparcos stars, and between 1 and 9430 for non-Hipparcos
     stars supplemented to the UCAC4 catalog (no CCD observation). For all
     other stars this unique star identification number is the internal
     mean-position-file (MPOS) number + 1million. Note, there are several
     thousand cases where different UCAC4 stars link to the same Hipparcos
     star number due to resolved binary stars with each component being a
     separate star entry in UCAC4.
Note (11): For each 2MASS bandpass a combined flag was created
     (cc_flg + ph_qual) consisting of the contamination flag (0 to 50)
     and the photometric quality flag (0 to 8).
       0 =  cc_flg 2MASS '0', no artifacts or contamination
      10 =  cc_flg 2MASS 'p', source may be contaminated by a latent image
      20 =  cc_flg 2MASS 'c', photometric confusion
      30 =  cc_flg 2MASS 'd', diffraction spike confusion
      40 =  cc_flg 2MASS 's', electronic stripe
      50 =  cc_flg 2MASS 'b', bandmerge confusion
       0 = no ph_qual flag
       1 = ph_qual 2MASS 'X', no valid brightness estimate
       2 = ph_qual 2MASS 'U', upper limit on magnitude
       3 = ph_qual 2MASS 'F', no reliable estimate of the photometric error
       4 = ph_qual 2MASS 'E', goodness-of-fit quality of profile-fit poor
       5 = ph_qual 2MASS 'A', valid measurement, snr>10 AND cmsig<0.10857
       6 = ph_qual 2MASS 'B', valid measurement, snr> 7 AND cmsig<0.15510
       7 = ph_qual 2MASS 'C', valid measurement, snr> 5 AND cmsig<0.21714
       8 = ph_qual 2MASS 'D', valid measurement, no snr OR cmsig req.
     For example the value 05 is decoded to be cc_flg=0, and ph_qual=5,
     meaning no artifacts or contamination and 2MASS qual flag = "A".
Note (12): Data are from the AAVSO Photometric all-sky survey (APASS) DR6
     plus single observation stars kindly provided by A.Henden. For bright
     stars the Bmag and Vmag columns contain the Hipparcos/Tycho Bt and Vt
     mags respectively, whenever there is no APASS B or V available and
     valid Bt or Vt mags were found. The errors flagged with "-" are formal
     errors estimated from the S/N, while the "normal" errors (flagged with
     ".") are from the official release data error estimates (at least 2
     observations per star).
Note (13): The g-flag from the Yale San Juan first epoch Southern
     Proper Motion data (YSJ1, SPM) has the following meaning:
     0 = no info
     1 = matched with 2MASS extended source list (2MASX
     2 = LEDA  galaxy
     3 = known QSO
Note (14): The c-flag from the Yale San Juan first epoch Southern Proper
     Motion data (YSJ1, SPM) indicates which input catalog has been used
     to identify stars for pipeline processing:
     1 = Hipparcos (Cat. I/311)
     2 = Tycho2 (Cat. I/259)
     3 = UCAC2 (Cat. I/289)
     4 = 2MASS psc (Cat. II/246)
     5 = 2MASS xsc (extended sources, Cat. VII/233; largely galaxies)
     6 = LEDA  (confirmed galaxies, Paturel et al. 2005)
     7 = QSO   (Veron-Cetty & Veron 2006, Cat. VII/248)
Note (15): The FK6-Hipparcos-Tycho-source-flag has the following meaning:
     0 = not a Hipparcos or Tycho star
     1 = Hipparcos 1997 version main catalog (Cat I/239)
     2 = Hipparcos double star annex
     3 = Tycho-2 (Cat. I/259)
     4 = Tycho annex 1
     5 = Tycho annex 2
     6 = FK6 position and proper motion (instead of Hipparcos data)
     7 = Hippparcos 2007 solution position and proper motion (Cat. I/311)
     8 = FK6, only PM substitution (not in UCAC4 data)
     9 = Hipparcos 2007, only proper motion substituted (Cat. I/311)
Note (16): The catflg match flag is provided for major catalogs used
     in the computation of the proper motions.  Each match is analyzed
     for multiple matches of entries of the 1st catalog to 2nd catalog
     entries, and the other way around.  Matches are also classified
     by separation and difference in magnitude to arrive at a confidence
     level group.  The flag has the following meaning:
     0 = star not matched with this catalog
     1 = unique-unique match, not involving a double star
     2 = unique-unique match, but involving a flagged double star
     3 = multiple match but unique in high confidence level group, no double
     4 = as 3, but involving a flagged double star
     5 = closest match, not involving a double, likely o.k.
     6 = closest match, but involving a flagged double star
     7 = maybe o.k. smallest separation match in both directions, no double
     8 = as 7, but involving a flagged double star
Note (17): value is either 0 (no match) or contains the log of the apparent
     total diameter (in 0.1arcmin) for I-band (object size) information
     copied from the LEDA catalog (galaxies). A size value of less than 1
     has been rounded up to 1.
Note (18): This flag is either 0 (no match) or contains the length of the
     semi-major axis of the fiducial ellipse at the K-band (object size)
     information copied from the 2MASS extended source catalog.
Acknowledgements:
    It is a pleasure to thank Norbert Zacharias, who wrote most of
    this introduction and answered to many questions.
History:
  * 01-Aug-2012: Original version
  * 30-Jan-2013 (version 'A'): Fix 3416 high proper motion stars
    The fix concerns 3416 stars in 416 binary zone files between
    6 and 449. All affected stars have object type flag = 4, i.e.
    stars observed with the astrograph and mean position and proper
    motion taken from external catalogs. Only the proper motion
    columns are affected by this bug, all other data items of those
    stars remain as they are in the UCAC4. The Python script file
    "modifs.py" patches the original zone files.
================================================================================
(End)         Norbert Zacharias [USNO], Francois Ochsenbein [CDS]    24-Jul-2012