Evolution of the opening angle of the orbit with and without precession. Opening angle is defined as the angle between the Earth–Typhon vector and the mutual orbit normal. Mutual events occurring at or near periapsis are visible with opening angles between maximum of ±8﹩\mathop{.}\limits^{{\unicode{x000b0}}}﹩7 (light red region), while events at or near apoapsis are visible between ±2﹩\mathop{.}\limits^{{\unicode{x000b0}}}﹩7 (darker red region).