S/N for a 4° ×4° FYST [CII] LIM mock survey of t_surv = 4000 hours. It consists of four tomographic scans of 40 GHz bandwidth each centered at z = 3.7, 4.3, 5.8, and 7.4. The S/N combines three effects: the instrumental white noise, the sample variance within each k-bin, and the attenuation due to smoothing by the instrumental beam. Lines are color-coded according to the used SFR-to-L_[CII] relation, blue lines for A20, green lines for L18, and black lines for V15. The magenta painted area represents the S/N > 1 values for the minimum Δk considered (Δk = 0.034 Mpc⁻¹, main y-axis), whereas the purple painted area denotes the S/N > 1 values for the maximum Δk considered (Δk = 0.34 Mpc⁻¹, secondary y-axis). Gray areas cover all k values for which as indicators for the transition scale between the clustering dominated to the shot noise dominated scales.