Subset of synthetic spectra of V746 Cas (black line) for the nominal model with χ² = 157 756 compared to the normalized observed ones (blue error bars). Only a region between 408 and 450 nm is shown, with a number of indicative lines: H_δ, HeI, SiII, SiII, HeI, CII, H_γ, HeI, HeI, and MgII. The synthetic spectra were interpolated to the observed wavelengths. The differences are denoted by red lines, or even red circles if the respective contribution to is larger than 100. Note it is difficult to improve the solution because our N-body model does not fit the spectra one-by-one or individual lines, but rather fits all the spectra at once. For example, the problematic synthetic spectrum of H_γ in the middle of the figure cannot be simply shifted to the left. These systematics may at least partly be caused by the rectification procedure.