This is the CONAD/GAIN conversion factor health check plot. The values are estimated from the FORS2 screen flats. For historical reasons (different control software) the CONAD and GAIN parameters are often confused. What is called CONAD here is really the GAIN parameter (units e-/adu).

If the exposure time of the first two raw screen flat fields in the input set of frames is the same (within 4%), the difference frame is computed. Then, the whole readout port is divided into a chessboard of 16x16 boxes. For each one of these boxes, the median signal level from the first raw frame is divided by the variance in the difference frame scaled by 2. The median value of the 16x16 values obtained is the accepted value for the conversion factor.

CONAD QC parameters are trended per readout mode for filter B only (historically B_BESS, now b_HIGH). More information can be found on the plot tutorial page

TPL.ID=img_cal_scrflat
DB Name: fors2_scrflat