Observations of the five coolest stars. The observed spectra are shown with black lines and the synthetic spectra with red lines. The blue ticks above the spectra indicate spectral features of H₂O whereas green marks OH(ν = 3 − 3) lines. Dashed lines mark the spectral features of interest which are ultimately used in the calculation of the formation region temperatures. In addition, one emission feature in the form of neutral Mg is visible at 818.1 cm^-1, and the HF line is also marked. The lack of observational data between the orders of the spectrometer, is indicated by the vertical solid black lines.