Magnitude difference between visits 3 and 49. Visit 49 is used as a reference. Although all the sources with an available measurement of their magnitude are shown, the sources we used to determine the aperture corrective factors have r(AB) magnitudes in the range 16–21. Dark and light gray dots represent magnitudes before and after the correction, respectively; similarly, the dashed and solid lines correspond to the average magnitude difference before and after the correction, respectively. The first defines the corrective factor, which in this case is ≈0.22. The obtained value varies depending on the visit seeing; it is higher for higher seeing values. Visit 3 has a seeing value of 104, which is one of the highest in our set of visits.