Degree of polarisation P_sca by scattering on non-spherical (oblate) dust grains as a function of the scattering angle Θ_sca and the polarisation P_ini of the incident radiation. The incident polarisation orientation is fixed to γ_ini = 0° (perpendicular to the symmetry axis S) and the grain axis ratio is c∕b = 1.5. The grain size is a_eff = 100 μm (left) and a_eff = 150 μm (right). Thescattering polarisation of an initially unpolarised wave on spherical grains is shown for comparison (black dotted lines).