Relation between the recovered σ(Hα) and the true σ(Hα) depending on the S/N. Panel a: relative errors for various S/N. Coloured areas encompass the 5th–95th percentile interval and dotted lines trace the median values. Panel b: probability density of absolute errors for S/N = 30. The adopted MUSE resolution at the wavelength of Hα is FWHM = 2.54 ± 0.1 Å (according to Bacon et al. 2017, but with twice larger scatter; vertical dashed line on panel a).