Top: core shift results as a function of frequency in the jet direction for CTA 102 at epochs 2005.4 (see Table 1). The red points correspond to the core shifts along the 2D path and the black ones to the core-shifts projected along the average PA of 90°. The solid curves represent a fit to the data with the formula Δr = Aν^{− 1 /k_r} + B and the values are given in the plot. Bottom: core shift in the sky plane. The red points correspond to the 2D path and the black points to the projection along the average PA of 90° shifted in the y-direction by −0.25 mas.