moonposition

Documentation

Overview

Moonposition: Chapter 47, Position of the Moon.

Index

• func Node(jde float64) unit.Angle
• func Parallax(Δ float64) unit.Angle
• func Perigee(jde float64) unit.Angle
• func Position(jde float64) (λ, β unit.Angle, Δ float64)
• func TrueNode(jde float64) unit.Angle

Examples

• Parallax
• Position

Functions

func Node

func Node(jde float64) unit.Angle

Node returns longitude of the mean ascending node of the lunar orbit.

func Parallax

func Parallax(Δ float64) unit.Angle

Parallax returns equatorial horizontal parallax of the Moon.

Argument Δ is distance between centers of the Earth and Moon, in km.

Example

package main

import (
	"fmt"

	"github.com/soniakeys/meeus/v3/julian"
	"github.com/soniakeys/meeus/v3/moonposition"
)

func main() {
	// Example 47.a, p. 342.
	_, _, Δ := moonposition.Position(julian.CalendarGregorianToJD(1992, 4, 12))
	π := moonposition.Parallax(Δ)
	fmt.Printf("π = %.6f\n", π.Deg())
}

Output:

π = 0.991990

func Perigee

func Perigee(jde float64) unit.Angle

Perigee returns longitude of perigee of the lunar orbit.

func Position

func Position(jde float64) (λ, β unit.Angle, Δ float64)

Position returns geocentric location of the Moon.

Results are referenced to mean equinox of date and do not include the effect of nutation.

λ  Geocentric longitude.
β  Geocentric latidude.
Δ  Distance between centers of the Earth and Moon, in km.

Example

package main

import (
	"fmt"

	"github.com/soniakeys/meeus/v3/julian"
	"github.com/soniakeys/meeus/v3/moonposition"
)

func main() {
	// Example 47.a, p. 342.
	λ, β, Δ := moonposition.Position(julian.CalendarGregorianToJD(1992, 4, 12))
	fmt.Printf("λ = %.6f\n", λ.Deg())
	fmt.Printf("β = %.6f\n", β.Deg())
	fmt.Printf("Δ = %.1f\n", Δ)
}

Output:

λ = 133.162655
β = -3.229126
Δ = 368409.7

func TrueNode

func TrueNode(jde float64) unit.Angle

TrueNode returns longitude of the true ascending node.

That is, the node of the instantaneous lunar orbit.