Telluric correction highlighted for an out-of-transit exposure during the first observation night on 2012-11-11. Upper panel: applied model of telluric lines. Middle panel: uncorrected flux in red and the corrected flux in black, which cannot be distinguished. We note the different scales for the two panels. Lower panel: difference between the corrected and uncorrected spectra for better visualisation. The impact of tellurics in the wavelength range of the cores of the sodium doublet is negligible. Nonetheless, a good telluric correction is crucial to clean the continuum baseline used for normalisation and where more telluric lines are situated.