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I/90        Positions of 502 Stars in Pleiades Region     (Eichhorn+ 1970)
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Accurate Positions of 502 Stars in the Region of the Pleiades
    Eichhorn H., Googe W.D., Lukac C.F., Murphy J.K.
   <Mem. Roy. Astron. Soc. 73, 125 (1970)>
   =1970MmRAS..73..125E
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ADC_Keywords: Positional data ; Clusters, open ; Regional catalog

Description:
    The catalog contains the positions (equinox B1900.0 and epoch B1955.0)
    of 502 stars in a region of about 1.5 degrees square in the Pleiades
    cluster, centered on Eta Tau. These coordinates have been derived from
    measurements of stellar images obtained with 65 exposures of various
    durations on 14 photographic plates with two telescopes at McCormick
    Observatory and Van Vleck Observatory. The plates were reduced by the
    plate overlap method, which resulted in a high degree of systematic
    accuracy in the final positions. Data in the machine version include
    Hertzsprung number, color index, photovisual magnitude, right
    ascension and declination and their standard errors, proper motion,
    and differences between the present position and previous works.
    Data for exposures, plates, and images measured, present in
    the published catalog, are not included in the machine version.


File Summary:
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  FileName   Lrecl  Records   Explanations
--------------------------------------------------------------------------------
ReadMe          80        .   This file
catalog.dat     80      502   The catalogue (Tables III and IV of the paper)
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See also:
  I/163 : US Naval Observatory Pleiades Catalog (van Flandern, 1969)

Byte-by-byte Description of file: catalog.dat
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   Bytes Format Units   Label     Explanations
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   1-  4  I4    ---   Hertzsprung Number in Hertzsprung's (1947) catalogue
   5-  8  F4.2  mag     CI        Colour index
   9- 14  F6.2  mag     Ptm       Photovisual magnitude
  15- 16  I2    h       RAh       Right Ascension, Equinox=B1900, Epoch=1955.0
                                    (hours)
  18- 19  I2    min     RAm       Right Ascension B1900 (minutes)
  21- 26  F6.3  s       RAs       Right Ascension B1900 (seconds)
  28- 30  I3    0.1ms e_RAs       Standard error on RA
      31  A1    ---     DE-       Declination, Equinox=B1900, Epoch=1955.0
                                    (sign)
  32- 33  I2    deg     DEd       Declination B1900 (degrees)
  35- 36  I2    arcmin  DEm       Declination B1900 (minutes)
  38- 42  F5.2  arcsec  DEs       Declination B1900 (seconds)
  43- 45  I3    mas   e_DEs       Standard error on DE
  47- 50  F4.2  ---     rmsRA     r.m.s. value for RA (1)
  52- 55  F4.2  ---     rmsDE     r.m.s. value for DE (1)
  56- 59  I4 0.1mas/yr  rpmRA     ? Relative Proper motion in RA (2)
  61- 64  I4 0.1mas/yr  rpmDE     ? Relative Proper motion in DE (2)
  66- 68  I3 0.1mas/yr  DrpmRA    ? Difference in rpmRA with Hertzsprung (1947)
  70- 72  I3 0.1mas/yr  DrpmDE    ? Difference in rpmDE with Hertzsprung (1947)
  74- 76  I3 0.01arcsec DRA       ? Difference in RA with Koenig (1924)
  78- 80  I3 0.01arcsec DDE       ? Difference in DE with Koenig (1924)
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Note (1): the r.m.s. values are defined by
     rms = sqrt(Sum((o-c)^2^/sigma^2^)/(n-1))
     where    n is the number of plates,
            (o-c) is the residual and
            sigma the actual error of the measurements on each plate
    A large rms value means therefore an agreement worse than expected on
    the basis of the weighting of the individual measurements, and a small
    rms an agreement better than expected.
    The product  e_RAs x rmsRA (resp. e_DEs x rmsDE) is then a good
    approximation of the dispersion of the individual contributing
    positions around their mean.

Note (2):
    The values of the proper motions are not compatible with the FK4 system.
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References:
    Hertzsprung E., 1947, Ann. Sterrew. Leiden 19, 1A   =1947AnLei..19....0H
    Koenig A., 1924, Astron. Nachr., 222, 177           =1924AN....222..177K

Historical Notes:
  * The catalogue was received in 1978 from Dr J. Sibol; no attempt has
    been made to verify the contents since the published catalogue was
    published from a machine-readable data set.
    The electronic catalogue was documented in 1979 by Theresa A. Nagy
    for NASA Greenbelt (document R-SAW-7/79-32)
  * 25-Sep-1995: Description added at ADC
  * 02-Jan-1996: Documentation completed at CDS according to standards.
  * 28-Dec-1999: Note (2) added from ADC version
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(End)                                     Francois Ochsenbein [CDS]  02-Jan-1996