[vsnet-chat 3375] V348 Sgr comparison stars

["Bruce Sumner" <b.sumner@bom.gov.au>]

Sebastian Otero asked for a comparison table to check the magnitudes 
in the field of V348 Sgr. Here is the data. I will leave it to others
to make any analysis.

GSC         UCAC1  AAVSO  Heck  Tycho err   Tycho  err
             'V'           V      V          B-V	
6858-02252  10.77        10.75  10.49 0.07   0.93  0.11
6858-02278  10.36               10.52 0.08   1.26  0.21
6858-01964  11.19  110   11.05  10.87 0.09   0.62  0.10
6858-01727  10.78  109   11.06			
6858-02920  11.73        11.54  11.23 0.13   0.57  0.15
6858-02438  11.72  115   11.48  11.41 0.15   0.41  0.14
6858-01425  11.80               11.42 0.16   0.54  0.18
6858-02962  11.91        11.77  11.69 0.20   0.41  0.19
6858-02176  11.00  106          11.75 0.24  -0.32  0.09

The V (PEP) magnitudes are from Heck et.al., A&AS,61,375H,1985, 
and are the means from several nights observations. Errors are 
quoted as being < +/-0.04 mag. 

The UCAC1 'V' values are from the polynomial regression: 
V=0.027U**2 - 0.666U + 3.784, were U is the raw UCAC1 magnitude.

I have included the errors for the Tycho-2 magnitudes, as 
suggested by Brian Skiff, so that an indication of the accuracy 
of the derived Tycho-2 magnitudes can be obtained.

Note that GSC 6858-01727 is quite red (b-y=1.10, Heck, et.a al.) 
and was therefore not measured during the Tycho experiment. The 
UCAC1 'V' magnitude for this star would thus also be about 0.2 
too bright.

The Tycho-2 magnitude of 11.75 for GSC 6858-02176 appears 
to be about 1 magnitude too faint, as a check of the 4 minute 
SERC-V DSS image (20 July 1987) will show.

Bruce Sumner

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