[vsnet-campaign-dn 594] (fwd) Survey calibration near NSV 10934

[Taichi Kato <tkato>]

Date: Fri, 16 Mar 2001 17:55:48 -0700 (MST)
From: Brian Skiff <bas@lowell.edu>
Subject: [vsnet-alert 5783] Survey calibration near NSV 10934

     In re survey photometry near NSV 10934, the only available data nearby
is the GSPC1 sequence S010; there is no GSPC2 data for the field yet.  For the
fainter stars we have the following:

Name       B      R      GSC     mb    mr
S010-C   12.03  11.21   12.14   11.5  11.3
S010-D   12.66  11.84   12.65   11.8  11.9
S010-E   13.64  11.94   13.31   12.6  12.0
S010-F   14.27  13.32   14.01   13.7  13.0
S010-G   16.43  14.75    ---    15.8  14.6

...where B and R are standard magnitudes, GSC is from the GSC, and mb and mr
are from USNO-A2.0 (not A1.0).
     The GSC magnitudes were derived from IIIa-J plates, and so are _blue_
magnitudes, not visual or red.  As can be seen, roughly speaking the GSC
magnitudes are not too far from standard B.  Note I have chosen the fainter
of the available GSC magnitudes for the same stars in the overlap region;
the "brighter" ones are about a quarter of a magnitude off.
     For A2.0, we see that the blue magnitudes are too bright by about
0.7 mag., but with a lot of scatter (not unusual on these bright stars, which
would be very much overexposed on the deep survey plates).  The red magnitudes
are not so bad, and at the faint end of the sequence run a couple tenths too
bright.
     Thus for unfiltered CCD observations, it is likely that adopting the
USNO-A2.0 red magnitudes will put you not far from standard R if the comp stars
are in the range of 'mr' 12 to 15.

\Brian

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