Quadrupole moment C_20,1 vs. the tidal time lag ∆t₁ of the central body. The corresponding values are plotted as colours (cyan, blue, white, and orange) and as numbers (gray). SKY and AO datasets were used. Models were converged for 195 combinations of the fixed parameters; all other parameters were free. For each combination, 1000 iterations were computed, that is, 195 000 models in total. Homogeneous body with C_20,1 = −0.1586 is excluded. Preferred solutions are either ≃−0.20, or ≃−0.12, indicated by red and green circles.