Upper panel: a typical raw HARPS spectrum (consecutive orders plotted with a different colour for better visibility). Lower panel: the same spectrum after order merging, normalisation, and the removal of cosmics which were not removed by the standard pipeline (with the average of all spectra also plotted in red). Signal-to-noise levels are also plotted order-by-order and for the merged spectrum. Detailed explanation of the process can be found in the text.