Spectroscopic sequence from 9500 to 21 500 Å. The spectral sequence covers the evolution of the photospheric (top) and nebular (bottom) phases. The NIR spectra at > 1 μm show only a few features in contrast to the optical spectra (Fig. 6). The most prominent features are labelled. All spectra were rebinned to 5 Å and smoothed with a Savitzky–Golay filter, except the spectrum at t_max+361.6 days that was rebinned to 10 Å. The grey scale at the bottom of each panel displays the strength of telluric features (white = transparent, black = opaque). In addition, regions of strong atmospheric absorption are grey-shaded.