Cross-correlation results obtained on the night N_{A, 1} for HD 209458 b (top row) and after combining four transits of HD 189733 b (bottom row). Left column: S/N maps of potential water vapour signals with respect to the exoplanet rest-frame (horizontal axis) and K_p (vertical axis). Middle column: slice through the left panels at the K_p with the largest significance peak for HD 209458 b (145 km s⁻¹) and at the expected K_p of HD 189733 b. Right column: cross-correlation matrices in the Earth rest-frame for the observed data and after injecting a signal at 3× the expected strength. The transit occurs between the cyan horizontal dashed lines. The cyan tilted dashed lines mark the expected velocities of the exoplanets during the observations. The tilted red dashed line in the case of HD 209458 b marks the position of the most significant signal observed.