TARDIS spectral model (blue) for the observations of SN1999em (black) taken by Hamuy et al. (2001) on the 9th of November. We have smoothed the Monte Carlo spectrum using a Savitzky–Golay filter (Savitzky & Golay 1964). The observational data has been taken from the WISeREP archive (Yaron & Gal-Yam 2012) and has been de-reddened according to the Cardelli et al. (1989) law with a color excess of E(B − V)=0.08 (http://www.weizmann.ac.il/astrophysics/wiserep/). To account for the peculiar velocity of the host galaxy, the observations have been blueshifted by 770 km s⁻¹ (see Leonard et al. 2002). Finally, the synthetic spectrum has been scaled to match the observed de-reddened flux f_λ. The main telluric features are marked with circled crosses.