Example of the one-dimensional χ² mapping used to derive uncertainties of orbital elements for the ξ Tau system. The dependencies of the χ² values on the three nodes Ω₁, Ω₂, Ω₃ are shown, while the remaining elements correspond to the best-fit values from Table 15. The preferred solution for Ω₁ ≃ 331°, with χ² = 2578, and a hint of a mirror solution at Ω₁ ≃ 151° are clearly visible. If the latter is optimised separately, we would obtain χ² as low as 2 749. The sudden increase of corresponds to the disappearance of the eclipses of the inner binary, which naturally results in extreme O−C’s.