Intensity I as a function of distance from the pointing centre due to a combination of bandwidth and time smearing over the original intensity at the pointing centre I₀. We used the smearing formulas according to Bridle & Schwab (1999) with a central frequency of 140 MHz and a bandwidth of 12.21 kHz. This plot includes the smearing from the longest baseline (1980 km) between the LOFAR stations in Birr (Ireland) and Łazy (Poland), reaching a resolution of about 0.2″ (red). We also added I/I₀ for our target resolution of 0.3″ (blue), corresponding to a baseline of 1470 km. This figure shows both the smearing for the 1 s and 2 s pre-averaged datasets.