Section of the SB2 spectrum. Top panel: Normalised flux of the first epoch (green), second epoch (orange), and combined (purple) spectra. The mean model, $\overline{S}$, is shown as a solid black line. The spectra are shifted vertically for clarity. Middle panel: Normalised flux errors, σ_F, of the three spectra shown in the panel above, with the same colour coding. The solid black line is the standard deviation of our model, ${\sigma }_{\overline{S}}$, i.e. it shows where our ensemble of models exhibits large variation, and hence uncertainty. Bottom panel: Normalised pixel weights, W, as defined in Eq. (12). Regions with higher values provide more constraints on our final ż measurement.