Trajectory of a lensing star in equatorial coordinates between 2008 and 2020 (black arrow). If a background source star (small star) lies inside the area defined with a minimal angular width 2w and the corner points 1 to 4, the lens (big star) will be identified as candidate in our table “Candidates for Astrometric Lensing”. The rectangle is a simplification of the trapezium (dashed lines), which expresses the increasing uncertainty in the lens positions and proper motions from the catalog epoch 2000.0.