Compact source and synthesized beam size as a function of right ascension (red, lower x-axis) and declination (blue, upper x-axis). The synthesized beam (transparent ‘×’ symbols) size for each LoTSS-DR2 pointing is the average of the major and minor FWHM of a fitted Gaussian. The compact source size (transparent circles) is the median of the average of the major and minor FWHM of the compact sources (according to Eq. (2)) with S/N greater than 20 in each mosaic. The marker sizes are proportional to the image rms (accounting for the flagging fraction and integration time) which is a proxy of data quality. The solid lines and larger markers show the median of both the synthesized beam (solid ‘×’ symbols) and compact source (solid circles) sizes as a function of right ascension (red) and declination (blue) and the errors show the corresponding standard deviations. The dashed black line shows the size of the restoring beam which is kept constant over the entirety of LoTSS-DR2 and is generally larger than the synthesized beam.