TSI reconstructed with various reference series using the following images: RP Ca II K and RP blue (a); RP Ca II K and RP red (b); RPS CA II K and RPS red (c); and SF Ca II K and RP blue (d). Colours are the same as in Figure 5. The solid line is 81-day running mean values for the series with PMOD as the reference, while the grey shaded surface shows the range covered by the reconstructions with all other TSI reference series. The dashed and dotted lines are linear fits to the reconstructed and reference TSI values, respectively, during subsequent activity minima. All series were offset to match their mean value within a 12-month interval centered at the minimum of 2008 to that of the PMOD TSI composite. The value of the PMOD TSI composite over this period is marked with the horizontal dash-dotted pink line. The various dashed and dotted lines extend only to the intervals for which their respective data cover the complete two surrounding minima.