Flare background light curves (top row) and their corresponding S/N vs. background cut threshold plots (bottom row). The leftmost panels are for a typical observation with notable background flaring. The second pair of vertically aligned panels shows an example where the background has a persistently low level, while the third pair of panels reflects an example where the background is persistently high. The rightmost panels show an example of a variable background which gives rise to a double-peaked S/N vs. background-rate-cut curve. The vertical red lines in the lower panels indicate the optimum background-cut-threshold (i.e. the peak of the curve) derived for the light curves in the top panels. In the upper panels the applied optimum cut-rate is also shown in red as horizontal lines.