Model of the RM and CLV effects in the transmission spectrum of MASCARA-1b around the Na I D2 line. Each panel shows the model computed with the parameters from Hooton et al. (2022) (black) and the models computed when one of the main parameters is changed to its upper (coloured dotted line) and lower (coloured dashed line) uncertainty value. The error bars of the model derived from the uncertainties of all these parameters are shown in grey.