Comparison of the effects of the light-time and Galactic acceleration on the position in the Galactic plane. The Sun is situated at x = y = 0, with the Galactic centre on the x axis. The curves show where the two effects are equal for the tangential velocity indicated (in km s^-1) next to the curve. The light-time effect exceeds that of the Galactic acceleration for stars closer to the Sun than the curves. Beyond the curves, the effect of the Galactic acceleration is more significant.