astro::moon_phase::illumination Namespace Reference

Functions
auto	phase_angle (const toolbox::SphericalCoordinate &sun_pos, const toolbox::SphericalCoordinate &moon_pos) -> toolbox::AngleDeg
	Compute the Moon's selenocentric phase angle i from two positions, Meeus (48.2)+(48.3).
auto	phase_angle (const double jde) -> toolbox::AngleDeg
	Compute the Moon's selenocentric phase angle i at a JDE, Meeus (48.2)+(48.3).
auto	position_angle (const astro::coords::EquatorialCoord &sun_eq, const astro::coords::EquatorialCoord &moon_eq) -> toolbox::AngleDeg
	Compute the position angle χ of the Moon's bright limb, Meeus (48.5).
auto	position_angle (const double jde) -> toolbox::AngleDeg
	Compute the position angle χ of the Moon's bright limb at a JDE, Meeus (48.5).
auto	fraction (const toolbox::AngleDeg &i) -> double
	Compute the illuminated fraction k of the Moon's disk from the phase angle, Meeus (48.1).
auto	fraction (const double jde) -> double
	Compute the illuminated fraction k of the Moon's disk at a JDE, Meeus (48.1).

Function Documentation

fraction() [1/2]

auto astro::moon_phase::illumination::fraction ( const double jde ) ->double

inlinenodiscard

Compute the illuminated fraction k of the Moon's disk at a JDE, Meeus (48.1).

Parameters

jde	The Julian Ephemeris Day, on the TT scale.

Returns

k in [0, 1] — 0 at new moon, 1 at full moon.

fraction() [2/2]

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

inlinenodiscard

Compute the illuminated fraction k of the Moon's disk from the phase angle, Meeus (48.1).

Parameters

i	The selenocentric phase angle.

Returns

k in [0, 1].

See also

Jean Meeus, "Astronomical Algorithms", Second Edition, Chapter 48.

phase_angle() [1/2]

auto astro::moon_phase::illumination::phase_angle ( const double jde ) ->toolbox::AngleDeg

inlinenodiscard

Compute the Moon's selenocentric phase angle i at a JDE, Meeus (48.2)+(48.3).

Parameters

jde	The Julian Ephemeris Day, on the TT scale.

Returns

The phase angle i, in [0°, 180°].

Positions: VSOP87D (Sun) and truncated ELP2000-82B (Moon), both apparent geocentric.

See also

Jean Meeus, "Astronomical Algorithms", Second Edition, Chapter 48.

phase_angle() [2/2]

auto astro::moon_phase::illumination::phase_angle ( const toolbox::SphericalCoordinate & sun_pos, const toolbox::SphericalCoordinate & moon_pos )->toolbox::AngleDeg

inlinenodiscard

Compute the Moon's selenocentric phase angle i from two positions, Meeus (48.2)+(48.3).

Parameters

sun_pos	The Sun's position, in any spherical frame shared with moon_pos (in-library: apparent geocentric ecliptic).
moon_pos	The Moon's position, same frame as sun_pos.

Returns

The phase angle i, in [0°, 180°] — 0° at full moon, 180° at new moon.

Note

The spherical law of cosines is frame-agnostic, so equatorial (α, δ) plugs into (λ, β) as-is — the golden test feeds the book's equatorial worked values directly.

See also

Jean Meeus, "Astronomical Algorithms", Second Edition, Chapter 48.

position_angle() [1/2]

auto astro::moon_phase::illumination::position_angle ( const astro::coords::EquatorialCoord & sun_eq, const astro::coords::EquatorialCoord & moon_eq )->toolbox::AngleDeg

inlinenodiscard

Compute the position angle χ of the Moon's bright limb, Meeus (48.5).

Parameters

sun_eq	The Sun's apparent geocentric equatorial coordinates (α₀, δ₀).
moon_eq	The Moon's apparent geocentric equatorial coordinates (α, δ).

Returns

χ in [0°, 360°), measured eastward from the north point of the disk.

Note

The formula uses equatorial coordinates; the spherical geometry is identical to (48.2), so the ecliptic-to-equatorial conversion must use the true obliquity for apparent places.

See also

Jean Meeus, "Astronomical Algorithms", Second Edition, Chapter 48.

position_angle() [2/2]

auto astro::moon_phase::illumination::position_angle ( const double jde ) ->toolbox::AngleDeg

inlinenodiscard

Compute the position angle χ of the Moon's bright limb at a JDE, Meeus (48.5).

Parameters

jde	The Julian Ephemeris Day, on the TT scale.

Returns

χ in [0°, 360°), measured eastward from the north point of the disk.

Sun: VSOP87D apparent equatorial; Moon: truncated ELP2000-82B apparent ecliptic, converted to equatorial with the true obliquity.

See also

Jean Meeus, "Astronomical Algorithms", Second Edition, Chapter 48.