Passbands used to perform the transmission light curves of HD 189733b (upper panel) and WASP-69b (lower panel). One observed spectrum is shown on the top of each panel and the ratio between this single in-transit spectrum and the master out is shown on the bottom. The blue regions mark the three different bandwidths (0.75 Å, 1.5 Å and 3.0 Å) centered at the line cores of D1 and D2, and the blue and red reference passbands used to measure the relative flux and calculate the transmission light curves are shown in gray. We note that, for WASP-69, only the D2 line is used.