Intensity and polarisation maps for the disc centre dataset. Panel a: continuum intensity map normalisedto the average continuum intensity. Magenta and yellow lines mark the solar latitude and longitude, respectively. The x- and y-axes show the observed distance on the solar disc in arcseconds. I_c is the average continuum intensity of disc centre quiet Sun. Panel b: map of the maximum linear polarisation signals at the blue wing of the 15 648.5 Å spectral line (given by ). Panel c: map of the maximum amplitude Stokes V at the blue wing of the 15 648.5 Å spectral line.