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tokens: of the observations. Notes .The airmass column contains the value at the start and end of the observations. The seeing value is corrected for the airmass and corresponds to the seeing at the zenith. Table 2. Comparison of the modelling parametrization of the telluric correction methods. Notes .Molecfit and TelFit packages allow for fitting the atmospheric transmission to the target spectrum. A summary of the capabilities and models employed by each package is shown in Table 2 . Appendix A presents the spectra of the telluric standard and the synthetic transmission spectra obtained with each of the packages. 3.1. TelFit The Python package TelFit ( Gullikson et al. 2014 ) models the atmospheric transmission and fits it to a spectrum with the Levenberg–Marquardt algorithm. TelFit can adjust the wavelength solution of the data to the telluric lines or vice versa with a polynomial function. The order of the polynomial can be set by the user, but the values of the coefficients have to be directly set in the code. TelFit offers a parametric model of the line shape through a Gaussian function and a non-parametric model with the singular value decomposition mode. For each observation, TelFit uses, by default, an average atmospheric profile for mid-latitudes. The website of the Global Data Assimilation System (GDAS) 6 enables the use of a custom atmospheric profile, adapted to the location and time of the observations. The GDAS profiles are available for observations taken since 2004 and are updated every three hours. We used the atmospheric profile that was closest to our observations, with a time difference inferior to 2 h, to first fit the spectrum of the standard star. We experimented with the parametric and non-parametric options for the line shape and attained the same level of correction. Since the other models studied in this work use parametric correction, and to provide a more meaningful comparison, we selected the parametric correction. To perform the fit of the standard star, we left the parameters of the wavelength solution, the continuum level, line shape, resolution, and the mixing ratio of the molecule relevant for the wavelength range considered (H 2 O or O 2 ) as free parameters. TelFit does not allow a different parametrization of spectral orders separated by wavelength gaps. Therefore, each of the three CRIRES detectors is treated independently because the parameters of the wavelength solution differ from one detector to the other. As such, for each fit we obtain a different value for the following parameters: molecule abundances, resolution, temperature, and pressure profiles. We homogenize these parameters by taking their mean values weighted by the inverse of the χ 2 calculated for each detector. Then, we use the homogenized values of the parameters to compute a final atmospheric transmission for each detector. We divide the stellar spectrum by the atmospheric transmission to correct for the telluric lines. After the