Simulations to study the influence of the stellar populations and the S/N on the measurement of the radial velocities. We plot the relative uncertainty when measuring the radial velocities Δv/v, defined as (v_o − v_i)/v_i) as a function of the S/N. Only the results for the radial velocity v = 1500 km s^-1 are shown because the offsets and errors found are independent of the radial velocity of the galaxy. The results plotted are for a typical dwarf galaxy with velocity dispersion of 40 km s^-1 and metallicity −0.4. The velocity dispersion does not have any effect on either the measurement of radial velocities or the metallicities. Note the different scale in the y-axis compared to Figs. 2 and 3.