Each read was subtracted from the first read, which was taken as a baseline. A 5x50 pixel array [499:503,441:490] near the center of the detector that was approximately uniformly illuminated was used for this analysis. A 3 sigma iterative rejection was used when calculating the statistics of each read.
(Top Panel) Flux versus integration time is plotted for each individual pixel in the 5x50 array. A linear equation is fit to the first 6 data points for each individual pixel, while an exponential equation is fit to data points 6 through 10. The last three data points are clearly saturated and not used for any fit. It is obvious that there are two distinct fits for both types of equations due to the offsets between even and odd rows in the detector. Two separate fits are listed on the right-hand side of the panel.
(Bottom Panel) Flux versus integration time is plotted for the average of all of the pixels at each integration time. The first frame is not included in this average, due to it typically being offset from the rest of the points. This left a total of 18 frames for the average. Again, a linear and exponential fit is shown. The average fits lay somewhere in between the individual pixel fits, as would be expected. The equations stated on the right-hand side can be used to show how the detector is approximately 1% non-linear at a flux value of ~5050 DN. Looking at the first read for each frame, the counts value is ~ 10,850 DN in the same 5x50 pixel array, which would mean that the detector response becomes 1% non-linear at a count value of ~5800 DN.
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