CCF contrast as a function of wavelength in the case where telluric contamination is considered, in the presence of a grey opacity source simulating large condensates at various pressure levels. Upper panel: high-resolution models of a hot Jupiter with T = 1700 K. Each colour corresponds to a different value of p_c, ranging between 10⁻⁷ and 1 bar, and the lightest colours correspond to condensates deeper in the atmosphere. Lower panel: CCF contrast as a function of wavelength. The colours are in correspondence with the models shown in the upper panel. For each value of p_c, the temperature range 1200–2300 K is explored. We indicate with a vertical error bar the induced variation in the contrast of the CCF. On the left, the 1σ precision of HARPS (blue), ESPRESSO (green), GIANO (orange, red, and black) for the Y, J, and H bands for a single transit are shown. These error bars only account for photon noise, but telluric residuals may introduce additional noise (see Appendix A).