Example of the comparison between TAPAS predictions and a CRIRES spectrum of the hot star β CMa. Top: three transmittance spectra of H₂O, N₂O, and CO₂ computed by TAPAS and before convolution are shown (right scale). Bottom: Data (in black) fit to the product of their convolved product by a fifth-order polynomial (green curve). The fit polynomial is displayed separately (red curve). The central gap in the data is due to the transition between the second and third detector of the instrument. Middle: differences between the data and the model expressed as the percentage of the fit continuum. The two broad and shallow features marked by S cannot be residual telluric features and are very likely stellar.