Comparison of the frequencies extracted from the three different spectral lines in the original observed spectra of 20 CVn with the values deduced from the LSD-based model spectra (for the Sc II 5239 Å only, based on the data sets characterized by different S/N) and from the LSD profiles themselves. The symbols refer to the three observables used for the analysis: the first- and third-order moments (squares and circles, respectively), and the profiles themselves (triangles). The frequency errors are assumed to correspond to the Rayleigh limit of the data. The vertical dashed line represents the literature value of 8.2168 d^-1 (Rodriguez et al. 1998).