Top panel: observed astrometric positions of GJ 338 B (blue dots) around the star GJ 338 A (black star located at 0,0 coordinates) expressed in Δδ vs. Δα cosδ. The black ellipse (dashed line) corresponds to the adopted Keplerian solution, which lies close to the region of the largest concentration of possible MCMC solutions. The oldest data and most recent astrometric data correspond to the year 1821 and 2019, respectively. Inner panel: zoom-in around the astrometric data. Only the adopted orbital solution is shown with the black dashed line. Bottom panel: residuals (± 0′′.11 in Δα cosδ and ± 0′′.14 in Δδ) after removing the adopted orbital solution plotted as a function of observing epoch (Δα cos δ: blue dots; Δδ: red dots).