Location and width of first-order secular resonances for the satellite. Each panel is plotted for one fixed value of the planet’s obliquity ε from 0° (left) to 90° (right). Resonances are labelled in the leftmost panel by their respective critical angle ξ (omitting the Q indexes). The coloured intervals show the extremal values of equatorial inclination I_Q spanned by the resonance separatrix. Inside each resonance, a conserved quantity links I_Q to the eccentricity e, as shown by the colour gradient.