Positional residuals from the model (O−C) as a function of x_raw and y_raw, respectively from top to bottom. Black points refer to the x residuals, while red points represent the y residuals. The gray dashed line in each plot is set at 0 for reference. The left panels show the O−C at the first iteration of the astrometric fit, while the right panels display the residuals at the last iteration of the fit (less points are visible because of the iterative rejection of outliers; see the text for details). In the top panels, we report the standard deviation (σ_O−C and the absolute maximum scatter of the points (|∆_O−C|) as a reference.