Top: Individual pointing ‘matched RMS’ as a function of observation date (green) together with the raw RMS measured from the images. The ‘matched RMS’ is the raw RMS adjusted to account for observation elevation, duration and bandwidth differences; it is scaled to match an 8 h 231 sub-band observation at optimal elevation $({\sigma }_{\mathrm{Matched}}={\sigma }_{\mathrm{Measured}}\times cos{(\pi /2-ϵ)}^2\times {\left(\frac{(1-F)\times T\times N_{\mathit{SB}}}{8.0\times 231}\right)}^{0.5})$, where ϵ is the elevation, F is the fraction flagged, T is the observation duration in hours, and N_SB is the number of sub-bands. Also plotted is the flagging fraction and the daily total number of sunspots (Clette & Lefèvre 2015) which gives an indication of the solar activity throughout the observing range. Middle: RMS adjusted to account for observation duration and bandwidth demonstrating that the expected elevation dependence is observed. Bottom: Histogram of the raw and matched RMS values.