// Planet computes UT rise, transit and set times for a planet on a day of
// interest.
//
// yr, mon, day are the Gregorian date.
// pos is geographic coordinates of observer.
// e must be a V87Planet object for Earth
// pl must be a V87Planet object for another planet.
//
// Obtain V87Planet objects with the planetposition package.
//
// Result units are seconds of day and are in the range [0,86400).
func Planet(yr, mon, day int, pos globe.Coord, e, pl *pp.V87Planet) (tRise, tTransit, tSet unit.Time, err error) {
jd := julian.CalendarGregorianToJD(yr, mon, float64(day))
α := make([]unit.RA, 3)
δ := make([]unit.Angle, 3)
α[0], δ[0] = elliptic.Position(pl, e, jd-1)
α[1], δ[1] = elliptic.Position(pl, e, jd)
α[2], δ[2] = elliptic.Position(pl, e, jd+1)
return Times(pos, deltat.Interp10A(jd), Stdh0Stellar,
sidereal.Apparent0UT(jd), α, δ)
}
func ExampleTimes_computed() {
// Example 15.a, p. 103, but using meeus packages to compute values
// given in the text.
jd := julian.CalendarGregorianToJD(1988, 3, 20)
p := globe.Coord{
Lon: unit.NewAngle(' ', 71, 5, 0),
Lat: unit.NewAngle(' ', 42, 20, 0),
}
// Th0 computed rather than taken from the text.
Th0 := sidereal.Apparent0UT(jd)
// Venus α, δ computed rather than taken from the text.
e, err := pp.LoadPlanet(pp.Earth)
if err != nil {
fmt.Println(err)
return
}
v, err := pp.LoadPlanet(pp.Venus)
if err != nil {
fmt.Println(err)
return
}
α := make([]unit.RA, 3)
δ := make([]unit.Angle, 3)
α[0], δ[0] = elliptic.Position(v, e, jd-1)
α[1], δ[1] = elliptic.Position(v, e, jd)
α[2], δ[2] = elliptic.Position(v, e, jd+1)
for i, j := range []float64{jd - 1, jd, jd + 1} {
_, m, d := julian.JDToCalendar(j)
fmt.Printf("%s %.0f α: %0.2s δ: %0.1s\n",
time.Month(m), d, sexa.FmtRA(α[i]), sexa.FmtAngle(δ[i]))
}
// ΔT computed rather than taken from the text.
ΔT := deltat.Interp10A(jd)
fmt.Printf("ΔT: %.1f\n", ΔT)
h0 := rise.Stdh0Stellar
tRise, tTransit, tSet, err := rise.Times(p, ΔT, h0, Th0, α, δ)
if err != nil {
fmt.Println(err)
return
}
fmt.Printf("rising: %+.5f %02s\n", tRise/86400, sexa.FmtTime(tRise))
fmt.Printf("transit: %+.5f %02s\n", tTransit/86400, sexa.FmtTime(tTransit))
fmt.Printf("seting: %+.5f %02s\n", tSet/86400, sexa.FmtTime(tSet))
// Output:
// March 19 α: 2ʰ42ᵐ43.25ˢ δ: 18°02′51.4″
// March 20 α: 2ʰ46ᵐ55.51ˢ δ: 18°26′27.3″
// March 21 α: 2ʰ51ᵐ07.69ˢ δ: 18°49′38.7″
// ΔT: 55.9
// rising: +0.51766 12ʰ25ᵐ26ˢ
// transit: +0.81980 19ʰ40ᵐ30ˢ
// seting: +0.12130 02ʰ54ᵐ40ˢ
}
func ExampleApproxTimes_computed() {
// Example 15.a, p. 103, but using meeus packages to compute values
// given in the text.
jd := julian.CalendarGregorianToJD(1988, 3, 20)
p := globe.Coord{
Lon: unit.NewAngle(' ', 71, 5, 0),
Lat: unit.NewAngle(' ', 42, 20, 0),
}
// Th0 computed rather than taken from the text.
Th0 := sidereal.Apparent0UT(jd)
fmt.Printf("Th0: %.2s\n", sexa.FmtTime(Th0))
// Venus α, δ computed rather than taken from the text.
e, err := pp.LoadPlanet(pp.Earth)
if err != nil {
fmt.Println(err)
return
}
v, err := pp.LoadPlanet(pp.Venus)
if err != nil {
fmt.Println(err)
return
}
α, δ := elliptic.Position(v, e, jd)
fmt.Printf("α: %.2s\n", sexa.FmtRA(α))
fmt.Printf("δ: %.1s\n", sexa.FmtAngle(δ))
h0 := rise.Stdh0Stellar
tRise, tTransit, tSet, err := rise.ApproxTimes(p, h0, Th0, α, δ)
if err != nil {
fmt.Println(err)
return
}
fmt.Printf("rising: %+.5f %02s\n", tRise/86400, sexa.FmtTime(tRise))
fmt.Printf("transit: %+.5f %02s\n", tTransit/86400, sexa.FmtTime(tTransit))
fmt.Printf("seting: %+.5f %02s\n", tSet/86400, sexa.FmtTime(tSet))
// Output:
// Th0: 11ʰ50ᵐ58.09ˢ
// α: 2ʰ46ᵐ55.51ˢ
// δ: 18°26′27.3″
// rising: +0.51816 12ʰ26ᵐ09ˢ
// transit: +0.81965 19ʰ40ᵐ17ˢ
// seting: +0.12113 02ʰ54ᵐ26ˢ
}
func ExamplePosition() {
// Example 33.a, p. 225. VSOP87 result p. 227.
earth, err := pp.LoadPlanet(pp.Earth)
if err != nil {
fmt.Println(err)
return
}
venus, err := pp.LoadPlanet(pp.Venus)
if err != nil {
fmt.Println(err)
return
}
α, δ := elliptic.Position(venus, earth, 2448976.5)
fmt.Printf("α = %.3d\n", sexa.NewFmtRA(α))
fmt.Printf("δ = %.2d\n", sexa.NewFmtAngle(δ))
// Output:
// α = 21ʰ4ᵐ41ˢ.454
// δ = -18°53′16″.84
}
// ApproxPlanet computes approximate UT rise, transit and set times for
// a planet on a day of interest.
//
// yr, mon, day are the Gregorian date.
// pos is geographic coordinates of observer.
// e must be a V87Planet object for Earth
// pl must be a V87Planet object for another planet.
//
// Obtain V87Planet objects with the planetposition package.
//
// Result units are seconds of day and are in the range [0,86400).
func ApproxPlanet(yr, mon, day int, pos globe.Coord, e, pl *pp.V87Planet) (tRise, tTransit, tSet unit.Time, err error) {
jd := julian.CalendarGregorianToJD(yr, mon, float64(day))
α, δ := elliptic.Position(pl, e, jd)
return ApproxTimes(pos, Stdh0Stellar, sidereal.Apparent0UT(jd), α, δ)
}