Schematic representation of the model. The dashed line represents the path followed by the target star photocentre (α_ast, δ_ast in Table 1) on the sky plane, as seen from a certain site. The stars are represented by the yellow dots; the size of the dot is proportional to the brightness. The origin on the sky plane (black dot) is determined by the theoretical astrometric position of 2007 OC10 according to our reference ephemeris. In this particular configuration of parameters, the site for which the chord is represented would observe the occultation, with a residual flux in the drop of f₁ (secondary star occulted, primary star visible).