Top: calibration between the pixel and wavelength values of the VLTI/AMBER observations of MWC 297. A least-square polynomial fit of the data is also shown (red line). Bottom: residuals between the measured position of the telluric line spectrum obtained from the wavelength calibration of the AMBER data and the expected position from the reference telluric spectrum provided by NOAO. The root-mean square value is of the order of 2.5   km   s^-1.