Effect of relativistic correction on posterior probability distributions of luminosity distances for the first epoch spectrum. The elementary supernova model is shown in orange and the same model including the relativistic corrections of Hutsemekers & Surdej (1990) is shown in light blue. For the mildly relativistic regime these systematic corrections are within the uncertainties of the distance. Cosmological redshift distances are also plotted for H₀ = 67.36 ± 0.54 (Planck Collaboration VI 2020) (dotted purple) and H₀ = 73.03 ± 1.04 (Riess et al. 2022) (dotted blue).