[vsnet-chat 809] Re: vsnet mail

[Taichi Kato <tkato>]

Regarding USNO-based magnitudes:

Berto Monard wrote:

> the USNO charts: as I said it's often the only reference some of us have,
> just wondering about their photometric accuracy...

   This is true for us for most northern fields, too.  From my experience
on several fields, USNO A1.0-derived magnitudes are at least as accurate
(as inaccurate ..) as GSC magnitudes.  If we are using GSC magnitudes as
temporary standards, there seems to be no reason to reject USNO-derived
magnitudes.  Sounthern USNO fields sometimes look less accurately
calibrated than northern fields (some fields have all stars having color
index greater than +5, or some stars may have b-r = -2).  Disregarding
these "anomalies", USNO-derived magnitudes can be used for observations
under similar cautions as in using GSC.

Regards,
Taichi Kato

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