[vsnet-chat 2386] Re: SN1999em magnitude discordance (Santallo)

[aah@nofs.navy.mil]

As Brian Skiff has pointed out, GSC magnitudes in this
field are B-like and therefore, compared with USNO-A r-magnitudes,
your results will be quite different depending on the
catalog.  There are three sequences currently being
used:  GSC (wrong since it is blue); USNO-A (ok for
unfiltered CCD, though with large scatter per star;
and AAVSO (an admixture of photoelectric and USNO-A).
  I actually have a photometric night tonight and am
just about ready to measure the field.  I'll post
a revised .dat file tomorrow if someone wants to parse
it and create a normal sequence like those posted
by Bruce Sumner.
Arne

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