Observed star spectrum (with dots where sampled) corrected from the H₂O transmission computed by TAPAS with the nominal value of H₂O (black curve), and also with 1.3 (green) and 1.5 the nominal H₂O value. The remaining self-reversal is a sign of inadequate resolution/line width. Even over this small spectral interval, it seems that the adequate factor to obtain a featureless spectrum after correction would need a different quantity of H₂O: while at 695.36 nm, the factor 1.3 would be approximately correct (green curve), it is too large at 695.64 nm. The TAPAS transmission spectrum is in blue, at the top, left scale, computed for 1.5 the nominal H₂O content.