Photometric sums from RP Ca II K (top), red (middle), and blue (bottom) observations. Daily values are shown in black, while 180-day running averages are shown in red. We note that the photometric sum indices were adjusted, following the method by Nesme-Ribes et al. (1996), to take into account the bias of the QS level (see Sect. 3). The dashed orange line shows the 180-day running average of the photometric sums prior to this adjustment, while the dash-dotted ciel line (only for the continuum data) was obtained following the approach by Preminger et al. (2002). The dashed blue horizontal line denotes the 0-level of photometric sum.