Comparison of the parameters determined with PASTEL catalogue average values for the well-known stars presented in Table 4. These plots endorse the ETOILE code for atmospheric parameter determination for red giant stars in the optical spectral region. Only stars with σ_Teff< 200 K, σ_log (g)< 0.5, σ_{[ Fe / H ]}< 0.2 from the PASTEL catalogue were selected as good-quality candidates to validate the method. Below the plots of T_eff, log(g), and [Fe/H] we plot the residuals, the residual dispersion is displayed in the respective plots.