[vsnet-newvar 1500] Re: [vsnet-chat 5407] Re: CGCS 2792

[Taichi Kato <tkato@kusastro.kyoto-u.ac.jp>]

Date: Sat, 20 Jul 2002 00:44:18 -0700 (MST)
From: Brian Skiff <Brian.Skiff@lowell.edu>

>>   CPD-62 1643 has a magnitide of 9.8 (CPD) V=10.96 (Tycho), which seem to
>> disagree with the value given in Buscombe.

     Buscombe almost certainly assumed the CD = CPD link, and took the
magnitude from "wherever" (he gives no citations in any of his compilations,
so source data are not recoverable).  Actually, the since the CPD magnitudes
are nominally photo-blue, the relevant match is 9.8 (CPD) and B=11.7 (Tycho-1).
This offset, however, is not at all unusual, since many of the fainter CPD
stars are mag. 12 or 13 in blue, though given as mag. ~10 in the CPD.
I consider this _good_, since it means the CPD has a lot of "interesting"
stars in it.  The lesson to be found of course is the sad state of magnitude
scales and zero-points that existed ~100 years ago, notably in the south.

\Brian

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