Meeus sunrise, sunset example

output

Sunrise:  6ʰ45ᵐ28ˢ
Sunset:   17ʰ11ᵐ46ˢ

sr.go

package main

import (
    "fmt"
    "math"

    "github.com/soniakeys/meeus/base"
    "github.com/soniakeys/meeus/globe"
    "github.com/soniakeys/meeus/julian"
    "github.com/soniakeys/meeus/rise"
    "github.com/soniakeys/meeus/sidereal"
    "github.com/soniakeys/meeus/solar"
)

// a quick check against values from USNO as computed at
// http://aa.usno.navy.mil/data/docs/RS_OneDay.php
//
// U.S. Naval Observatory
// Astronomical Applications Department
//
// Sun and Moon Data for One Day
//
// The following information is provided for Boston, Suffolk County,
// Massachusetts (longitude W71.1, latitude N42.3):
//
//        Wednesday
//        12 February 2014      Eastern Standard Time
//
//                         SUN
//        Begin civil twilight       6:16 a.m.
//        Sunrise                    6:45 a.m.
//        Sun transit               11:59 a.m.
//        Sunset                     5:13 p.m.
//        End civil twilight         5:42 p.m.

var (
    // USNO gives the coordiates it uses in decimal degrees, so I do a simple
    // conversion to radians like this rather than use base.NewAngle as in
    // examples in the package doc.
    bostonLon = 71.1 * math.Pi / 180
    bostonLat = 42.3 * math.Pi / 180

    h0 = rise.Stdh0Solar // events of interest are sunrise, sunset

    jd = julian.CalendarGregorianToJD(2014, 2, 12) // date of interest

    tz = -5 * 3600. // EST time zone correction, in seconds
)

func main() {
    p := globe.Coord{bostonLat, bostonLon}
    Th0 := sidereal.Apparent0UT(jd)
    ra, dec := solar.ApparentEquatorial(jd) // position of sun
    mRise, _, mSet, err := rise.ApproxTimes(p, h0, Th0, ra, dec)
    if err != nil {
        fmt.Println(err)
        return
    }
    fmt.Println("Sunrise: ", base.NewFmtTime(mRise+tz))
    fmt.Println("Sunset:  ", base.NewFmtTime(mSet+tz))
}