astro::planet::geocentric_coord Namespace Reference

Functions
auto	apparent (const Planet planet, const double jde_tt) -> toolbox::SphericalCoordinate
	Calculate a planet's apparent geocentric ecliptic position.
auto	is_retrograde (const Planet planet, const double jde_tt) -> bool
	Return whether a planet's apparent geocentric longitude decreases across one day centered on jde_tt.

Variables
constexpr double	PLUTO_START_JDE_TT
	Inclusive start of Pluto's apparent-position model, in JDE(TT).
constexpr double	PLUTO_END_JDE_TT
	Exclusive end of Pluto's apparent-position model, in JDE(TT).

Function Documentation

apparent()

auto astro::planet::geocentric_coord::apparent ( const Planet planet, const double jde_tt )->toolbox::SphericalCoordinate

inlinenodiscard

Calculate a planet's apparent geocentric ecliptic position.

Parameters

planet	The planet to calculate, from Mercury through Pluto.
jde_tt	The Julian Ephemeris Day based on TT.

Returns

Apparent longitude and latitude in the true ecliptic and equinox of date, and the retarded geocentric distance in AU.

Exceptions

std::invalid_argument	If jde_tt is not finite or outside the selected planet's documented domain, or planet is not a named enumerator.
std::runtime_error	If the numerical evaluation cannot produce a finite, converged position.

Note

Pluto is available for JDE(TT) [2409543.5, 2488069.5); the Mercury-Neptune models have no finite JDE(TT) range bound.

Includes light-time, annual aberration, FK5 reduction, and nutation. It omits relativistic light deflection and treats TT as the VSOP87D dynamical-time argument without a TT-TDB model.

See also

Jean Meeus, "Astronomical Algorithms", Second Edition, (23.2), (32.3), and (33.1)-(33.4).

is_retrograde()

auto astro::planet::geocentric_coord::is_retrograde ( const Planet planet, const double jde_tt )->bool

inlinenodiscard

Return whether a planet's apparent geocentric longitude decreases across one day centered on jde_tt.

Parameters

planet	The planet to calculate, from Mercury through Pluto.
jde_tt	The Julian Ephemeris Day based on TT.

Returns

true when the wrap-aware longitude change over the centered one-day interval is negative.

Exceptions

std::invalid_argument	If jde_tt is not finite or outside the selected planet's documented domain, or planet is not a named enumerator.
std::runtime_error	If either apparent-position evaluation cannot produce a finite, converged result.

Note

Pluto is available for centered JDE(TT) [2409544.0, 2488069.0).

This is a finite-interval test, not the sign of the instantaneous rate from astro::ephemeris::longitude_rate (ephemeris.hpp); near a station the two can disagree.

It does not locate stations. astro::planet::phenomena::events (planet_phenomena.hpp) finds them as longitude extrema on a one-day grid and refines each extremum, without solving for a zero rate. astro::ephemeris::stations instead locates zeros of the seven-point ephemeris::longitude_rate; see docs/EPHEMERIS_EVENTS.md for the definitions and domains. At the stationary instant itself a boolean direction is not physically meaningful.

Variable Documentation

PLUTO_END_JDE_TT

double astro::planet::geocentric_coord::PLUTO_END_JDE_TT

inlineconstexpr

Exclusive end of Pluto's apparent-position model, in JDE(TT).

PLUTO_START_JDE_TT

double astro::planet::geocentric_coord::PLUTO_START_JDE_TT

inlineconstexpr

Inclusive start of Pluto's apparent-position model, in JDE(TT).