Astrometric observations (red, green, blue, and magenta points for planets HR 8799e, d, c, and b, respectively) in the set used for the analysis. The thick gray curves illustrate the best-fitting orbits (Table 1). The light gray curves in the left panel mark the referencing circular orbits of radii 10, 20, 30, ..., 80 au in the orbital plane of the system. The red, blue, green, and magenta arrows point to the periastron of each orbit. The close-up of the GRAVITY data is illustrated in the inset in the top right corner of the left panel. Gray curves represent 200 randomly chosen orbits from the DE-MC sampling, and black dots mark positions at the orbits in the epoch of the GRAVITY observation (2018.656). The graph is centered at the datum, and the axes are expressed in milliarcseconds. Black curves are for 1σ, 2σ, and 3σ confidence intervals for the model position at the R.A.–decl. plane at the epoch of 2018.656, derived from the DE-MC sampling. The right panel illustrates the observations and model orbits as the time functions of R.A. and decl.