Measurement of the RASSINE line-depth precision using series of adjacent nights. The date of the first night forming a pair is indicated on the x-axis. For each night, the line depth was computed on the full spectrum, rejecting telluric regions. The weighted rms (coloured dots) was extracted from the distribution of the line-depth difference, where the difference is taken between two adjacent nights (see e.g. Fig. 7). The average rms ⟨rms⟩ on the night-to-night differences is measured and shown as horizontal solid lines. Left: 2008 α Cen B dataset. Middle: 2010 α Cen B dataset. Right: solar dataset.