Visualisation of the focus change due to HARPS ageing on the CCF FWHM and RV time series of HD 10700 obtained with the HARPS G2 mask. Top left: CCF FWHM time series of HD 10700. The star is known to be extremely quiet and the long-term trend observed is likely induced by the instrument ageing. The linear trend is about 1 m s⁻¹ year⁻¹, which proves the impressive stability of HARPS (and HD 10700) over a decade. A similar though decreasing trend is observed in the CCF contrast. Bottom left: RV difference obtained on the RV before and after applying the YARARA correction to the spectral time series. YARARA allows a long-term linear drift of 10 cm s⁻¹ year⁻¹ to be suppressed. Right: correlation plot of the previous time series, which shows the strong dependence between those two quantities, with a Pearson correlation coefficient of 0.82. The 21 cm s⁻¹ rms that we can see in the residuals can be explained by the simultaneous fit of the CCF contrast and CaII S-index along with the FWHM or bad fit on some wavelength columns.