Typical accuracy of the stellar continuum subtraction. Top panel: raw (gray), after correcting the low-frequency residuals (black) and synthetic spectra for a typical sample target. The correction of the low-frequency residuals are typically <5%. In this spectrum the correction is hardly visible. The correction is visible around 7000 Å, corresponding to a region typically affected by sky subtraction residuals. Lower panel: residuals after subtracting the synthetic spectrum.