astro::earth::nutation Namespace Reference

Classes
struct	θCoeffs
struct	ψCoeffs
struct	εCoeffs
struct	NutationCoeffs

Enumerations
enum class	Model : uint8_t { MEEUS , IAU_1980 }
	Specify Earth's nutation model. More...

Functions
auto	find_model (const Model model) -> std::span< const NutationCoeffs >
	Find the nutation coefficients for the given model.
auto	gen_eval_θ (const double jc)
	Return the function to calculate the θ values, for the given julian century.
auto	longitude (const double jde, const Model model=Model::IAU_1980) -> toolbox::AngleDeg
	Calculates the nutation in longitude (Δψ) for the given julian day.
auto	obliquity (const double jde, const Model model=Model::IAU_1980) -> toolbox::AngleDeg
	Calculates the nutation in obliquity (Δε) for the given julian day.

Variables
constexpr std::array< NutationCoeffs, 63 >	MEEUS_NUTATION_COEFFS
constexpr std::array< NutationCoeffs, 106 >	IAU1980_NUTATION_COEFFS

Enumeration Type Documentation

Model

enum class astro::earth::nutation::Model : uint8_t

strong

Specify Earth's nutation model.

Enumerator
MEEUS
IAU_1980

Function Documentation

find_model()

auto astro::earth::nutation::find_model ( const Model model ) ->std::span< constNutationCoeffs >

inlinenodiscard

Find the nutation coefficients for the given model.

gen_eval_θ()

auto astro::earth::nutation::gen_eval_θ ( const double jc )

inlinenodiscard

Return the function to calculate the θ values, for the given julian century.

Parameters

jc	The julian century since J2000.

Returns

The function to calculate the θ values, which takes θCoeffs as input and returns the θ value in degrees.

Note

Handed back as auto, not std::function: this evaluator runs once per coefficient row of the nutation table, so type erasure here buys an indirect call on every single term of every nutation evaluation (#98).

See also

Jean Meeus, "Astronomical Algorithms", Second Edition, Chapter 22.

longitude()

auto astro::earth::nutation::longitude ( const double jde, const Model model = Model::IAU_1980 )->toolbox::AngleDeg

inlinenodiscard

Calculates the nutation in longitude (Δψ) for the given julian day.

Parameters

jde	The julian ephemeris day number, which is based on TT.
model	The model to use when calculating the nutation. Defaults to Model::IAU_1980.

Returns

The nutation in longitude (Δψ) in degrees.

Note

Omission retains the fixed IAU 1980 convention.

Twin of nutation::obliquity, which sums the same table and differs in exactly two places: it reads coeffs.Δε and it takes the cosine. The duplication is deliberate — each body mirrors its own Meeus summation — so fix both or neither (#49).

See also

Jean Meeus, "Astronomical Algorithms", Second Edition, Chapter 22.

obliquity()

auto astro::earth::nutation::obliquity ( const double jde, const Model model = Model::IAU_1980 )->toolbox::AngleDeg

inlinenodiscard

Calculates the nutation in obliquity (Δε) for the given julian day.

Parameters

jde	The julian ephemeris day number, which is based on TT.
model	The model to use when calculating the nutation. Defaults to Model::IAU_1980.

Returns

The nutation in obliquity (Δε) in degrees.

Note

Omission retains the fixed IAU 1980 convention.

Twin of nutation::longitude, which sums the same table and differs in exactly two places: it reads coeffs.Δψ and it takes the sine. The duplication is deliberate — each body mirrors its own Meeus summation — so fix both or neither (#49).

See also

Jean Meeus, "Astronomical Algorithms", Second Edition, Chapter 22.

Variable Documentation

IAU1980_NUTATION_COEFFS

std::array<NutationCoeffs, 106> astro::earth::nutation::IAU1980_NUTATION_COEFFS

inlineconstexpr

MEEUS_NUTATION_COEFFS

std::array<NutationCoeffs, 63> astro::earth::nutation::MEEUS_NUTATION_COEFFS

inlineconstexpr