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Occurrence of Bright Sources with Large Uncertainties

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Below is a table of the number of bright sources in the entire
collection of 3-band wsdb "good" sources which have large sigmas
(greater than 0.10 in all bands).  The bright source data was
preselected to have ?_m<12.0.

  h_range          number

 11.0-12.0         16039
 10.0-11.0          2800   (1420 if the requirement is sigma>0.15 instead)
  9.0-10.0           488
  8.0- 9.0            63

Below is a color/mag and color/color diagram of the 10.0-11.0 sample.
Not surprisingly all of the sources are heavily reddened as would
be expected in a high source density region.  Very few sources fall
in the unreddened main-sequence region of the diagram (where precise
photometry is of great value).  Further, the dispersion across
the reddening vector is certainly less than 0.10 mag -- either
the color errors are correlated or the uncertainty is
being overestimated for these sources.