Relative weight of the low frequency and high frequency part of the noise and stellar signal. Top panel: PSDs of the high-pass filtered noise (in blue) and of the complementary low-pass filtered noise (in red). Bottom panel: Stellar spectrum PSD with the high-frequency part in blue and the low-frequency part in red. The star spectrum corresponds to a M-star and the tellurics to present a case where we have a strong high-frequency content.