Module nutation 

IAU 2000A nutation computation, ported from the C++ Skyfield-compatible implementation.

Originally pub(crate) inside orbis_nif; now public in the core crate so a Rust-only consumer can reach the transform substrate without Rustler or the BEAM. The numerics, summation order, and transcendental sequence are preserved exactly so the existing Skyfield 0-ULP parity holds.

All arithmetic uses plain operators (no f64::mul_add) so that rounding matches CPython / Skyfield compiled without FMA contraction.

Enums

NutationError

Error returned when public nutation inputs are outside the valid domain.

Functions

build_skyfield_nutation_matrix

Build the 3x3 nutation rotation matrix from mean obliquity, true obliquity, and the nutation in longitude (psi).

skyfield_equation_of_the_equinoxes_complimentary_terms

Complementary terms of the equation of the equinoxes, in radians.

skyfield_fundamental_arguments

Compute the five Delaunay fundamental arguments of nutation theory for a given Julian-century offset t from J2000.0 TDB.

skyfield_iau2000a_radians

Compute nutation in longitude (dpsi) and obliquity (deps) in radians using the full IAU 2000A model.

skyfield_mean_obliquity_radians

Mean obliquity of the ecliptic in radians for the given TDB Julian date.