Leftcolumn: S/N maps for HD 209458 b on the nights N_{A, 2} (top) and N_{A, 3} (bottom) for potential water signals with respect to the exoplanet rest-frame (horizontal axis) and K_p (vertical axis). The horizontal dashed lines mark the K_p = 0 km s⁻¹ value. Middle column: slice through the left panels at the expected K_p for HD 209458 b (146 km s⁻¹). Right column: cross-correlation matrices in the Earth rest-frame. The transits occur between the horizontal dashed lines. The tilted dashed lines trace the expected planet velocities during the observations.