Trend of (S/N)_θ as a function of . The baselines of the first and second measurements are fixed to 0.0 and 0.8. The solid coloured curves correspond to different values of . The black line shows the trend in case of equal S/N for the two measurements, the dashed black line the trend for the single measurement scenario (Sect. 3), and the horizontal dotted lines represent the maximum limit of each of the corresponding coloured curves. The scenario in which we fix the second measurement is not shown because it is completely symmetric.