From: Robert A. Knop Jr. (robert.a.knop@vanderbilt.edu)
Date: Thu Apr 11 2002 - 04:42:45 PDT
> objects. Hopefully the magnitudes are off. Well, I know the magnitudes
> are off (since the observers failed to get standard star observations
> last night, these magnitudes are based on APM magnitudes -- even though
> subaru doesn't use a standard I band filter!), but I hope that they
Note that the standard I-filter isn't the real issue with APM (really,
USNO) magnitudes. Those are based on plate scans of an emulsion
sensitive primarily to red light. I don't know what the "effective"
bandpass is, but the magnitudes were already a bit shaky for R-band
searches, and are terrible for I-band searches. Pick the R-I color of
an average field star, and that will give you an idea of the rough range
by which USNO magnitudes will be wrong-- though even with that
correction, I wouldn't trust the result to better than 0.8mag or so.
-Rob
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