Normalized spectra of WASP-69 (top) and HD 189733 (bottom) for night 1, in the region of the Na I doublet. Different flux offsets are added to each spectrum for a better visualization. In both cases, the spectra are organized by observing time: the first spectrum of the night is located in the upper position and the last one in the lowest position. For WASP-69 the airmass decreases with time and for HD 189733 it increases. In black are shown the out-of-transit spectra and in gray, the in-transit spectra. The blue regions show where the telluric sodium is observed for WASP-69 spectra and where the telluric sodium is expected for HD 189733 data. We note that the last spectrum of WASP-69 for the first night is not used in the reduction process because of the higher noise compared to other spectra of the same night.