Filename                               Reason     Bkg         V      RCAM      TCAM   Sigma
20210921.183622.ucomp.637.l1.p7.fts        16    23.0     18.22       0.3       0.2     NaN
20210921.190100.ucomp.637.l1.p7.fts        16    22.9     17.38       0.4       0.3     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 (45.0)
    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 (1000.0)
   64   the difference of the image with the median is above threshold (1.8)

* indicates that the threshold values changed on the day