/**
 * precession.ts — IAU 2006 precession and mean obliquity.
 *
 * The previous implementation approximated precession by *adding* the scalar
 * general-precession-in-longitude ψ_A to a J2000 ecliptic longitude. That is
 * not the transformation: the ecliptic pole itself moves, so the mapping is a
 * rotation, not a translation, and the scalar shortcut leaves a latitude-
 * dependent error that grows with distance from J2000.
 *
 * Here the transformation is done properly:
 *   ICRF equatorial  --P(t)-->  mean equator & equinox of date  --R1(ε_A)-->
 *   mean ecliptic & equinox of date
 *
 * Angles: Capitaine et al. (2003), adopted as IAU 2006. The constant terms in
 * ζ_A and z_A carry the ICRS→J2000 frame-bias rotation in right ascension; the
 * two residual bias components (ξ₀, η₀ ≈ 17 mas) are neglected, which is two
 * orders of magnitude below this engine's 1″ target.
 */
export type Vec = [number, number, number];
export type Mat = [Vec, Vec, Vec];
/** Julian centuries (TT) from J2000.0. */
export declare function julianCenturies(jd: number): number;
/**
 * Mean obliquity of the ecliptic (degrees), IAU 2006.
 *
 * ε_A = 84381.406″ − 46.836769″T − 0.0001831″T² + 0.00200340″T³
 *                  − 0.000000576″T⁴ − 0.0000000434″T⁵
 */
export declare function meanObliquity(T: number): number;
/**
 * Precession matrix P such that  v_meanEquatorOfDate = P · v_ICRF.
 *
 * P = R3(−z_A) · R2(θ_A) · R3(−ζ_A)
 */
export declare function precessionMatrix(T: number): Mat;
export declare function matVec(m: Mat, v: Vec): Vec;
/** Apply the transpose of `m` — for a rotation matrix this is the inverse. */
export declare function matTransposeVec(m: Mat, v: Vec): Vec;
/** Rotate about the x-axis by `angleDeg` (equatorial → ecliptic uses +ε). */
export declare function rotateX(v: Vec, angleDeg: number): Vec;
/** Cartesian → spherical. Returns longitude/latitude in degrees, radius in input units. */
export declare function toSpherical(v: Vec): {
    lon: number;
    lat: number;
    r: number;
};
/**
 * Transform an ICRF equatorial vector to the **mean** ecliptic and equinox of
 * date — the frame in which sidereal longitudes and ayanamsa are defined.
 */
export declare function icrfToMeanEclipticOfDate(v: Vec, T: number): Vec;
/**
 * Inverse of {@link icrfToMeanEclipticOfDate}: mean ecliptic of date → ICRF.
 */
export declare function meanEclipticOfDateToIcrf(v: Vec, T: number): Vec;