Comparison of the polarisation profiles of PSR B2217+47 between 3 observations: when the pulsar was at transit and 5 hours before and after transit. The transit observation corresponds to ≈84° elevation and those around transit, to ≈45°. a) Comparison between the polarisation-angle profiles, where the phase-independent offsets between the profiles are due to the parallactic rotation of the source with respect to the LOFAR antennas. b), c) Comparison between the linear and circular polarisation profiles, where the flux density has been normalised by the maximum flux value of the profile at transit. Below the profiles, the residual difference between the profiles around transit and that at transit is shown.