The amplitude of that term, in the equation for nutation in obliquity, which has the period of the longitude of the Moon's ascending node. Alternatively, the coefficient of cosΩ in the equation Δε = a cos Ω + b cos 2 Ω + c cos 2L`s + d cos 2L _m, in which Δε is the nutation in obliquity of the ecliptic, Ω is the longitude of the Moon's ascending node, L _s is the mean longitude of the Sun and L _m is the longitude of the Moon. The value adopted by the International Astronomical Union in 1976 is 9. 2109" at epoch 2000.