One of the worst cases (DT 5) of the effects of disentangling residuals of HD 152219 in He I 4922. Top, two left panels: Single spectra as observed on 2004 May 09 and on 2006 May 06. The two right panels show the average of the two spectra and of all nine spectra used, whereby each component has been shifted to RV = 0 before averaging. The black lines mark Gaussian fits to the profiles, with FWHM and height A_line labelled. Likewise, the peak-to-peak amplitude of the residual wiggles, A_res, is given, determined outside of the velocity range ±3σ of each profile marked by the coloured vertical bars. Averaging reduces the residual wiggles. Bottom: Fourier transform amplitude of the average of all nine spectra, for the primary (left panel), and for the secondary including and excluding residuals (middle and right panel, respectively). The details are explained in Sect. 3.2.3.