Histograms of the along-scan residuals normalised to the formal uncertainties for the accepted solutions with G_mag ≤ 11.5 shown in blue or G_mag > 11.5 shown in green. The histogram in magenta shows all sources (accepted or rejected) with G_mag ≤ 11.5. A Gaussian fit to the data is shown as well. We note that for sources with Gmag > 11.5, the distribution is very well represented by a Gaussian (μ = 0.018, σ = 1.08), but for G_mag ≤ 11.5, the distribution is clearly not Gaussian.