Modeling results of the kinematics for knot C4. It moves along a curved trajectory with small oscillations. Its inner trajectory and kinematics can be well fitted by the precessing nozzle model within core separation r_n < 0.58 mas. In the upper left panel the solid black line (modeling the inner trajectory) and the dashed red line (modeling the entire trajectory) coincide within core separation of 0.58 mas, showing the curvatures in its outer trajectory. In the upper right panel two additional modeled trajectories are shown for ejection epochs t₀   ±   0.5 yr, demonstrating that most of the observation data points are within the position angle range defined by the two trajectories (green and magneta lines) and the precession period is determined within an uncertainty of ~ ± 0.5 yr.