Illustration of different phases of the analysis. Upper left panel: evenly sampled light curve generated with β = −1.4. This curve was cut from a longer set ∼100 times longer than shown here. Lower left panel: simulated curve resampled to the observing epochs of Mkn 421 and with instrumental noise added. Right panel: likelihood curve of Mkn 421 with the MFVF. The maximum of the polynomial fit (solid line) corresponds to β = −1.38.