Model fitting of the kinematics for knot c: trajectory X_n-Z_n, core separation r_n(t), coordinates X_n(t) and Z_n(t), the modeled apparent velocity/viewing angle and Lorentz/Doppler factor. The inner trajectory with the core separation less than ~0.8 mas is fitted by the precessing jet-nozzle model and the outer trajectory is fitted by introducing changes of the amplitude function A(Z). In the upper plots, two additional (red and green) curves calculated for ejection times = t₀ + 0.3 yr and t₀−0.3 yr are shown, indicating that most of the observational data points are within the regions confined by the two curves and the precession period is determined with an uncertainty of ~0.3 yr.