Stellar velocity dispersion of aperture spectra obtained from the mock HARMONI observations relative to the stellar velocity dispersion of the HSIM_Inputs. Different symbols indicate the distinct hosts: circles → NGC 809, triangles → PGC 055442, and squares → NGC 7119A. Colours correspond to redshift and grating: blue filled symbols → z = 0.76, and IzJ grating; blue open symbols → z = 1.50, and IzJ grating; red filled symbols → z = 2.30, and HK grating. Grey dashed line marks the 20% level of uncertainty. Black dotted line indicates the typical uncertainty of σ_⋆ for the HSIM_Inputs. Black solid line indicates σ_OUTPUT = σ_INPUT.