Altitude profile with HARPS and method 1 without Ring correction (upper panel) and different empirical Ring corrections. The amount of correction is 1% of the continuum at 5880 Å: i) Noxon et al. (1979); ii) Noxon et al. (1979) except in deep telluric bands (T < 0.5) where the Ring effect is negligible because Raman-scattered photons are strongly absorbed (Sioris & Evans 2000); iii) a λ^-2 power law to mimic the chromatic dependance observed by Pallamraju et al. (2000) or Brinkmann (1968); iv) a λ^-2 power law subtracted except in deep telluric bands (T < 0.5); and v) a subtraction of the reciprocal of the spectrum (Johnston & McKenzie 1989), which mimics the Ring spectrum. Here again, the obtained Ring spectrum is not removed from deep telluric lines (T < 0.5). The Na I doublet peaks at ≈5890 Å for all types of Ring corrections tested.