Relative astrometry of HR 8799 planets. Overline are the Soummer et al. (2011) orbital solution for the outer planets and a coplanar circular orbital solution in 5:2 resonance for the inner planet (blue lines, Case A in Table 7). For HR 8799e, the dotted line shows the circular and coplanar orbital solution for 2:1 mean motion resonance with planet d, which does not fit the observations. Filled circles: literature results. Filled squares: data from the present paper. Red lines connect the predicted and observed position for all the data points.