Detected S/N (S/N_sp) in the Fourier spectra vs. the calibrated analytical S/N (S/N_an). Each star is characterized by its own calibration factor α and (S/N_an). The calibration has been derived from injected signal tests, as described in the text. The MACHO and K2 stars are plotted by black and magenta, respectively. Pale green and red rectangles denote the parameter regimes where the two S/N estimates yield consistent and inconsistent detection results, respectively.