Filename                               Reason     Bkg         V      RCAM      TCAM   Sigma
20210927.192021.ucomp.656.l1.p5.fts        40    -0.2      0.01    7197.2    6133.9     NaN
20210927.194941.ucomp.656.l1.p5.fts        40    -0.2      0.01    6367.0    6956.8     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 (800.0)
   64   the difference of the image with the median is above threshold (3.0)

* indicates that the threshold values changed on the day