Doppler maps of the He ii λ 4686 (left) and Hα (right) emission lines in the spectrum of LSS 3074. The crosses correspond to the radial velocity amplitudes of the centre of mass of the primary (negative ) and secondary (positive v_y), whereas the dashed lines indicate the Roche lobe in velocity space for a mass ratio m₁/m₂ = 0.86. The colour scale indicates the level of the line emissivity relative to its maximum value.