Offsets between the positions measured in 2015 and 2019 of the sources in Tables 2 and 3. The pulsar is source 17 and its offset (Δp) is plotted with a blue square. The centroid’s offset and the standard deviation of the reference sources around this value are shown with horizontal dotted lines. The grey area in each plot is the uncertainty of the centroid’s offset, as calculated using a bootstrap method. Top: results for RA and Dec obtained for 21 reference sources. Bottom: results obtained for the 17 reference sources that present offsets consistent with that of the centroid’s. The rejected sources are plotted with smaller red symbols and were not used to measure the centroid (see Table 4).