Projection of the real orbit onto the plane of the sky. The axes originate at Sgr A* (the focus of the ellipse). The picture illustrates the orbital parameters: ϕ is the azimuth angle of the spherical system of coordinates associated with the x, y, z Cartesian coordinates, i.e., for an elliptic motion in the x-y plane, it is the true anomaly, i is the angle of inclination between the real orbit and the observation plane, Ω is the angle of the ascending node, and ω is the argument of pericenter. It is worth noting that the Z-axis of the coordinate system is defined by the vector pointing from the Solar System to the Galactic center.