Comparison of methods for measuring the position of C1 in the 2019 data. Red curve corresponds to the relative intensity from the PCA image, while the blue curve corresponds to the centro-symmetrical self-subtraction of the disk, from the same PCA image. Both methods provide the same result ±0.2 au. The position was measured by doing a Gaussian fit on the peak. The two curves have been normalized to make the comparison more visible.