moon

Documentation

Overview

Moon: Chapter 53, Ephemeris for Physical Observations of the Moon.

Incomplete. Topocentric functions are commented out for lack of test data.

Index

• func Physical(jde float64, earth *pp.V87Planet) (l, b, P, l0, b0 unit.Angle)
• func SunAltitude(η, θ, l0, b0 unit.Angle) unit.Angle
• func Sunrise(η, θ unit.Angle, jde float64, earth *pp.V87Planet) float64
• func Sunset(η, θ unit.Angle, jde float64, earth *pp.V87Planet) float64

Examples

• Physical
• SunAltitude
• Sunrise

Functions

func Physical

func Physical(jde float64, earth *pp.V87Planet) (l, b, P, l0, b0 unit.Angle)

Physical returns quantities useful for physical observation of the Moon.

Returned l, b are librations in selenographic longitude and latitude. They represent combined optical and physical librations. Topocentric librations are not considered.

Returned P is the the position angle of the Moon's axis of rotation.

Returned l0, b0 are the selenographic coordinates of the Sun.

Example

package main

import (
	"fmt"

	"github.com/soniakeys/meeus/v3/julian"
	"github.com/soniakeys/meeus/v3/moon"

	pp "github.com/soniakeys/meeus/v3/planetposition"
)

func main() {
	j := julian.CalendarGregorianToJD(1992, 4, 12)
	earth, err := pp.LoadPlanet(pp.Earth)
	if err != nil {
		fmt.Println(err)
		return
	}
	l, b, P, l0, b0 := moon.Physical(j, earth)
	fmt.Printf("l = %.2f\n", l.Deg())
	fmt.Printf("b = %+.2f\n", b.Deg())
	fmt.Printf("P = %.2f\n", P.Deg())
	fmt.Printf("l0 = %.2f\n", l0.Deg())
	fmt.Printf("b0 = %+.2f\n", b0.Deg())
}

Output:

l = -1.23
b = +4.20
P = 15.08
l0 = 67.90
b0 = +1.46

func SunAltitude

func SunAltitude(η, θ, l0, b0 unit.Angle) unit.Angle

SunAltitude returns altitude of the Sun above the lunar horizon.

Arguments η, θ are selenographic longitude and latitude of a site on the Moon, l0, b0 are selenographic coordinates of the Sun, as returned by Physical(), for example.

Example

package main

import (
	"fmt"

	"github.com/soniakeys/meeus/v3/julian"
	"github.com/soniakeys/meeus/v3/moon"

	pp "github.com/soniakeys/meeus/v3/planetposition"
	"github.com/soniakeys/unit"
)

func main() {
	j := julian.CalendarGregorianToJD(1992, 4, 12)
	earth, err := pp.LoadPlanet(pp.Earth)
	if err != nil {
		fmt.Println(err)
		return
	}
	_, _, _, l0, b0 := moon.Physical(j, earth)
	h := moon.SunAltitude(
		unit.AngleFromDeg(-20), unit.AngleFromDeg(9.7), l0, b0)
	fmt.Printf("%+.3f\n", h.Deg())
}

Output:

+2.318

func Sunrise

func Sunrise(η, θ unit.Angle, jde float64, earth *pp.V87Planet) float64

Sunrise returns time of sunrise for a point on the Moon near the given date.

Arguments η, θ are selenographic longitude and latitude of a site on the Moon, jde can be any date.

Returned is the time of sunrise as a jde nearest the given jde.

Example

package main

import (
	"fmt"
	"time"

	"github.com/soniakeys/meeus/v3/julian"
	"github.com/soniakeys/meeus/v3/moon"

	pp "github.com/soniakeys/meeus/v3/planetposition"
	"github.com/soniakeys/unit"
)

func main() {
	earth, err := pp.LoadPlanet(pp.Earth)
	if err != nil {
		fmt.Println(err)
		return
	}
	j0 := julian.CalendarGregorianToJD(1992, 4, 15)
	j := moon.Sunrise(
		unit.AngleFromDeg(-20), unit.AngleFromDeg(9.7), j0, earth)
	y, m, d := julian.JDToCalendar(j)
	fmt.Printf("%d %s %.4f TD\n", y, time.Month(m), d)
}

Output:

1992 April 11.8069 TD

func Sunset

func Sunset(η, θ unit.Angle, jde float64, earth *pp.V87Planet) float64

Sunset returns time of sunset for a point on the Moon near the given date.

Arguments η, θ are selenographic longitude and latitude of a site on the Moon, jde can be any date.

Returned is the time of sunset as a jde nearest the given jde.