Left panels: the dependence on the inner eccentricity (e₁) of the amplitudes A_ℳ, of the functions ℳ, describing the long-period dynamical part of O−C for specific values of other orbital elements. To compare the ℳ and terms, the former should be multiplied by e₂. The thin lines (indexed by “1”) refer to the first-order approximation, and the thick ones (index “6”) to the sixth one. Right panels: the corresponding A_1,2,3 amplitudes of the trigonometric representation (Eq. (32)) of the O−C for two different outer eccentricities (e₂ = 0.3 and e₂ = 0.7) (g₂ was set to 0°).