Histograms of the retrieved phases of the second SN image using the absorption lines Fe II, Hα, and Hβ. The phase inference is done for S/N = 10, 20, and 30 and for noiseless spectra. The red vertical lines in the histograms indicate the epochs of the five available spectra of the first SN image. The thick vertical line marks the input value. By using the wavelengths of absorption features, the phase of the second SN image is correctly recovered. (a) Retrieved phase using the absorption line of Fe II. (b) Retrieved phase using the absorption line of Hα. (c) Retrieved phase using the absorption line of Hβ. (d) Retrieved phase combining all three absorption lines.