Category/number      VI Photometry of NGC 188     T von Hippel 1998
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WIYN Open Cluster Study 1: Deep Photometry of NGC 188
     von Hippel T., Sarajedini A.
     AJ, 116, 1789 (1998)
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ADC_Keywords: Clusters, open
Description:
     We present V and I broad-band photometry on the Johnson-Kron-Cousins
     (Landolt 1992) system for the central 6.7' x 6.7' field of the old
     open cluster NGC 188.  Only objects with a probability of >= 95% of
     being stellar based on SExtractor (Bertin & Arnouts 1996) analysis of
     0.7" I-band images are presented.  The resulting photometry of 750
     sources spans the range from V = 14 (just above the turn-off) to V =
     26.  We estimate the external accuracy (tie to the Landolt system) to
     be <= 0.01 mag for the brightest stars (V < 17) and <= 0.032 mag for
     the fainter stars blueward of V-I = 2.  Stars redder than V-I = 2
     required an extrapolation of our standard star solution.  Equatorial
     coordinates for equinox J2000 and epoch 1996.10 were kindly derived
     by Imants Platais, Yale University, using 160 reference stars from
     the HST Guide Star Catalog. The standard error of the coordinates is
     0.14", primarily limited by the accuracy of GSC star positions.

File Summary:
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FileName    Lrecl    Records   Explanations          
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ReadMe       80         .      This file                  
NGC188VI.dat 98       750      NGC 188 photometry VI data file
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Nomenclature Notes:
     The IDs are based on the IAU standard system and include the name of
     our collaboration, WOCS (WIYN Open Cluster Study), followed by J for
     J2000 coordinates, and then the coordinates themselves in RA+Dec
     notation.  For example, our first object is WOCS J0049562+851236 with
     coordinates RA=00:49:56.29 and Dec=+85:12:36.2 (J2000).

Byte-by-byte Description of file: NGC188VI.dat
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 Bytes   Format   Units* Label    Explanations              
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001-020  string                   IAU designation
022-023  A2       hours           RA, hours
025-026  A2       mins            RA, minutes
028-032  F5.2     secs            RA, seconds
034-035  A2       degs            Dec, degrees
037-038  A2       arcmins         Dec, minutes
040-043  F4.1     arcsecs         Dec, seconds
045-052  F8.3     pixels          CCD X position
054-061  F8.3     pixels          CCD Y position
063-069  F7.4     mags            V magnitude
071-075  F5.3     mags            IRAF estimated V magnitude error
077-077  A1                       number of V-bandpass measurements
079-085  F7.4     mags            I-magnitude
087-091  F5.3     mags            IRAF estimated I magnitude error
093-093  A1                       number of I-band measurements
095-098  F4.2     fraction        stellar classification probability
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References: 
   "UBVRI photometric standard stars in the magnitude range 11.5-16.0
   around the celestial equator.", 1992, Landolt, A.U., AJ, 104, 340

   "SExtractor: Software for source extraction.", 1996, Bertin, E.,
   Arnouts, S., 1996, A&AS, 117, 393
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