This plot shows the collected counts in zimpol flat frames. 
Only the values labeled 'I' coming from the illuminated rows and are scored.
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The QC parameter in Box 1 and in Box 3 measures the ADU in one layer of the raw frame
(including a BIAS level of ~950 ADU). This QC parameter checks that the flats
are not saturated. 
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Since 2015-06-01 QC parameter in Box 2 and Box 4 (S/N_CAMi) measures the square root of NDIT times the bias subtracted counts,
the signal-to-noise ratio. This QC parameter is not calculated by the pipeline
but by a QC script. <br>
 25000 ADU corresponds to a S/N of 50 <br>
10000 ADU corresponds to a S/N of 100 <br>
40000 ADU corresponds to a S/N of 200. 

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Box5 and Box7 show the rms of the layer also used for Box1 and Box3. </font><p><font size="2">
Box6 and Box8 show: rms of the raw frame cube plane medians. Meaning: take the
median of each plane/layer of the raw frame which comes as fits cube. Take the 
rms of this sample of median values. This parameter is sensitive to variations
in the flux level with time (along the third axis of the raw frame cube)