Filename                               Reason     Bkg         V      RCAM      TCAM   Sigma
20210921.183819.ucomp.691.l1.p7.fts        16    20.5    212.59       1.5       3.3     NaN
20210921.190307.ucomp.691.l1.p7.fts        16    20.3     32.39       2.2       2.4     NaN

GBU bitmask codes
Code    Description
    1   spar guide control loop is below threshold (0.99)
    2   spar guider intensity below threshold (0.9 * 6.551 * exp(-0.05 * secz))
    4   median background is above threshold (40.0)
    8   median background is below threshold (5.0)
   16   spurious Stokes V signal is above threshold (8.0)
   32   the chi-squared of the occulter fit is above threshold (800.0)
   64   the difference of the image with the median is above threshold (1.7)

* indicates that the threshold values changed on the day