Illustrations of the advantages of the method (symbols are the same as Fig. 2). Left: clear period determination, but it would be (erroneously) twice smaller if only the second order of the Fourier series was used. Center: two solutions with acceptable sigma values but corresponding to the same period – if the number of local maxima is taken into account. Right: all solutions below the significance level, thus, the uncertainty interval is 2–237 h, i.e., the period is not determined.