Comparison of the orientation of the projection of the magnetic field on the plane of the sky, in orthographic projection with the dust optical depth at 353 GHz as the coloured background, from optical data (top panels) and from Planck data at 353 GHz (bottom panels). The line length is proportional to the S/N on the polarization angle. Northern (left panels) and southern (right panels) Galactic hemispheres are shown, with the Galactic centre situated at the top of each map.