Radial velocity shift that had to be applied by ESP-HS in CU8 to align the theoretical spectrum to the observed RVS spectrum as determined by MTA. It is plotted as a function of the T_eff determined by ESP-HS. Top panel: running median (computed over consecutive T_eff bins of 10 K) and the interquantile dispersion (15.85%–84.15%) of this offset as a function of the effective temperature. Bottom panel: how many stars went into each 10 K bin.