Example of the MUSE spectra (black line) of [B86] 133 and of the corresponding XSL DR1 spectrum (red line; normalized to match the MUSE spectrum flux). The plot title lists the spectral type and the measured median S/N per resolution element over the entire spectrum. Upper sub-panels: spectra extracted from each individual exposure (shifted up for clarity) and average spectra of the object at its true flux level. Bottom sub-panels: standard deviation of the average spectrum. The spectra of the other sample stars are presented in Fig. A.1.