Implement apparent sidereal time (equation of the equinoxes)#12
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MattBlack85 wants to merge 3 commits intomainfrom
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Implement apparent sidereal time (equation of the equinoxes)#12MattBlack85 wants to merge 3 commits intomainfrom
MattBlack85 wants to merge 3 commits intomainfrom
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Add get_apparent_sidereal_time_from_date() to sidereal_time.rs. Apparent sidereal time = mean sidereal time + Δψ cos ε, where Δψ is nutation in longitude and ε is the true obliquity of the ecliptic (Meeus, Astronomical Algorithms 2nd ed., Ch. 12, p. 87-88). Also adds mean_obliquity() helper (Meeus eq. 22.2), a test against Example 12.a (1987 April 10), and a Criterion benchmark.
Replace the full 63-term IAU 1980 nutation series (126 trig calls) with the 4-term approximation from Meeus p. 88 (4 sin + 1 cos). Accurate to ~0.5" (~0.03s of time), which is sufficient for sidereal time purposes. Drops the nutation module dependency from sidereal_time.rs entirely.
…accuracy Replace the 4-term approximation with the full 63-term IAU 1980 nutation series, keeping accuracy while optimizing with three techniques: - Skip delta_eps/cos accumulation entirely (only Δψ is needed for the equation of the equinoxes) — halves trigonometric calls vs get_nutation - FMA (mul_add) chains for all argument and amplitude arithmetic - AVX2 SIMD (delta_psi_avx2_fma): batches arg computation and amplitude accumulation 4 rows at a time using _mm256_fmadd_pd; sin is still evaluated per-lane (std has no vectorised trig) Also tightens get_nutation to use sin_cos() so both components share a single trig call per row.
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Add get_apparent_sidereal_time_from_date() to sidereal_time.rs.
Apparent sidereal time = mean sidereal time + Δψ cos ε, where Δψ is
nutation in longitude and ε is the true obliquity of the ecliptic
(Meeus, Astronomical Algorithms 2nd ed., Ch. 12, p. 87-88).
Also adds mean_obliquity() helper (Meeus eq. 22.2), a test against
Example 12.a (1987 April 10), and a Criterion benchmark.