astro::illumination Namespace Reference

Namespaces
namespace	detail

Classes
struct	Geometry
	Observer-facing illumination geometry for a target body. More...

Functions
auto	fraction (const toolbox::AngleDeg &phase_angle) -> double
	Calculate the illuminated disk fraction from the target-centered phase angle.
auto	geometry (const toolbox::SphericalCoordinate &source_pos, const toolbox::SphericalCoordinate &target_pos) -> Geometry
	Calculate the angular separation, target-centered phase angle, and illuminated fraction.

Function Documentation

fraction()

auto astro::illumination::fraction ( const toolbox::AngleDeg & phase_angle ) ->double

inlinenodiscard

Calculate the illuminated disk fraction from the target-centered phase angle.

Parameters

phase_angle

The angle between source and observer as seen from the target.

Returns

Illuminated fraction in [0, 1] for a finite phase angle.

See also

Jean Meeus, "Astronomical Algorithms", Second Edition, Formulas (41.1) and (48.1).

geometry()

auto astro::illumination::geometry ( const toolbox::SphericalCoordinate & source_pos, const toolbox::SphericalCoordinate & target_pos )->Geometry

inlinenodiscard

Calculate the angular separation, target-centered phase angle, and illuminated fraction.

Parameters

source_pos	The illuminating body's observer-centered spherical position.
target_pos	The target body's position in the same spherical frame as source_pos.

Returns

The target's observer-facing illumination geometry.

Note

Distances must share one unit; the library's spherical coordinates carry AU.

Meeus prints these equations for the Moon; the distance-triangle identities are target-neutral, with the planetary analogues discussed in Chapter 41. His ecliptic form beneath (48.2) omits the Sun's latitude; the full spherical separation here keeps both latitudes.

See also

Jean Meeus, "Astronomical Algorithms", Second Edition, (48.1)-(48.3).