Simple sketch (not to scale) of the expanding and bipolar arrangement of RS Oph ejecta. The orbital plane is vertical and the viewing angle matches the i ∼ 50° ±5° inclination inferred from the radial velocity orbit and assumed masses for the RG and WD. For the definition of t_τ (about day +20) and the meaning of the other labels, see Sect. 3.2. The lower panel represents the view to RS Oph at the time of the day +34.3 EVN observation, when the leading edge of the receding lobe (EA) has moved past the projected distance from the centre where the free–free opacity of the DEOP in the foreground drops to τ_ν = 1.