High resolution measurements of the temperature dependence of the optical rotatory power ρ (T) in the SmC* phase of the ferroelectric liquid crystal DOBAMBC are presented. Special emphasis is on the region near the SmC*-SmA transition. These data together with measurements of the pitch allow for a determination of the molecular tilt angle in the helicoidal structure. This is believed to be the first optical measurement of the tilt in an unperturbed SmC* phase, i.e. without unwinding of the helix. The measurements of the tilt angle in this case are compared with those on the unwound structure and are briefly discussed in connection with theory.