Maximum expected signal-to-noise ratio S/N  vs. V-magnitude for a A0 V star with AURELIE grating N° 5 in the second order at 6000 Å. S/N  is given for four integration times: 5, 30, 60 and 120 min. The star is assumed at air mass unity and all the starlight is collected by the entrance hole. Moreover the factor p  = 2 (see Eq. (7).)