Uncertainty on astrocomb line centres from fitting our empirical IP models to the data, . Main panel: as a function of position on the detector. The colour bar zero point is set to the sample median, such that the red and the blue colours correspond to values larger and smaller than the median, respectively. Lines with larger uncertainties generally have larger (cſ. Fig. 9) or low S/N (at 500 nm). Top panel: Histogram of the values plotted in the main panel. The vertical dashed red lines show the median and the central 68% distribution limits, which are also shown as thick black horizontal lines in the colour bar. The x-axis on the top shows in units m s⁻¹ (1 pix = 820m s⁻¹).