The iterative calibration procedure fits the differential voltages with the expected dipolar signal (K_CMB), both projected on a map, and it calculates the gain according to Eq. (27). As Fig. 8 shows, depending on the position of the circle with respect to the axis of the dipole signal, the range spanned by the signal can be either large (dipole maximum, top) or small (dipole minimum, bottom). Of course, in the latter case the estimation of the gain suffers from a larger statistical error.