func ExampleInterp10A() {
// Example 10.a, p. 78.
dt := deltat.Interp10A(julian.CalendarGregorianToJD(1977, 2, 18))
fmt.Printf("%+.1f seconds\n", dt)
// Output:
// +47.6 seconds
}
// 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 ExampleTimes() {
// Example 15.a, p. 103.
jd := julian.CalendarGregorianToJD(1988, 3, 20)
p := globe.Coord{
Lon: base.NewAngle(false, 71, 5, 0).Rad(),
Lat: base.NewAngle(false, 42, 20, 0).Rad(),
}
// Meeus gives us the value of 11h 50m 58.1s but we have a package
// function for this:
Th0 := sidereal.Apparent0UT(jd)
α3 := []float64{
base.NewRA(2, 42, 43.25).Rad(),
base.NewRA(2, 46, 55.51).Rad(),
base.NewRA(2, 51, 07.69).Rad(),
}
δ3 := []float64{
base.NewAngle(false, 18, 02, 51.4).Rad(),
base.NewAngle(false, 18, 26, 27.3).Rad(),
base.NewAngle(false, 18, 49, 38.7).Rad(),
}
h0 := rise.Stdh0Stellar
// Similarly as with Th0, Meeus gives us the value of 56 for ΔT but
// let's use our package function.
ΔT := deltat.Interp10A(jd)
rise, transit, set, err := rise.Times(p, ΔT, h0, Th0, α3, δ3)
if err != nil {
fmt.Println(err)
return
}
fmt.Println("rising: ", base.NewFmtTime(rise))
fmt.Println("transit:", base.NewFmtTime(transit))
fmt.Println("seting: ", base.NewFmtTime(set))
// Output:
// rising: 12ʰ26ᵐ9ˢ
// transit: 19ʰ40ᵐ30ˢ
// seting: 2ʰ54ᵐ26ˢ
}
func ExamplePlanetary() {
// Example 18.a, p. 117.
// Day of month is sufficient for a time scale.
day1 := 5.
day5 := 9.
// Text asks for Mercury-Venus conjunction, so r1, d1 is Venus ephemeris,
// r2, d2 is Mercury ephemeris.
// Venus
r1 := []float64{
sexa.NewRA(10, 27, 27.175).Rad(),
sexa.NewRA(10, 26, 32.410).Rad(),
sexa.NewRA(10, 25, 29.042).Rad(),
sexa.NewRA(10, 24, 17.191).Rad(),
sexa.NewRA(10, 22, 57.024).Rad(),
}
d1 := []float64{
sexa.NewAngle(false, 4, 04, 41.83).Rad(),
sexa.NewAngle(false, 3, 55, 54.66).Rad(),
sexa.NewAngle(false, 3, 48, 03.51).Rad(),
sexa.NewAngle(false, 3, 41, 10.25).Rad(),
sexa.NewAngle(false, 3, 35, 16.61).Rad(),
}
// Mercury
r2 := []float64{
sexa.NewRA(10, 24, 30.125).Rad(),
sexa.NewRA(10, 25, 00.342).Rad(),
sexa.NewRA(10, 25, 12.515).Rad(),
sexa.NewRA(10, 25, 06.235).Rad(),
sexa.NewRA(10, 24, 41.185).Rad(),
}
d2 := []float64{
sexa.NewAngle(false, 6, 26, 32.05).Rad(),
sexa.NewAngle(false, 6, 10, 57.72).Rad(),
sexa.NewAngle(false, 5, 57, 33.08).Rad(),
sexa.NewAngle(false, 5, 46, 27.07).Rad(),
sexa.NewAngle(false, 5, 37, 48.45).Rad(),
}
// compute conjunction
day, dd, err := conjunction.Planetary(day1, day5, r1, d1, r2, d2)
if err != nil {
fmt.Println(err)
return
}
// time of conjunction
fmt.Printf("1991 August %.5f\n", day)
// more useful clock format
dInt, dFrac := math.Modf(day)
fmt.Printf("1991 August %d at %s TD\n", int(dInt),
sexa.NewFmtTime(dFrac*24*3600))
// deltat func needs jd
jd := julian.CalendarGregorianToJD(1991, 8, day)
// compute UT = TD - ΔT, and separate back into calendar components.
// (we could use our known calendar components, but this illustrates
// the more general technique that would allow for rollovers.)
y, m, d := julian.JDToCalendar(jd - deltat.Interp10A(jd)/(3600*24))
// format as before
dInt, dFrac = math.Modf(d)
fmt.Printf("%d %s %d at %s UT\n", y, time.Month(m), int(dInt),
sexa.NewFmtTime(dFrac*24*3600))
// Δδ
fmt.Printf("Δδ = %s\n", sexa.NewFmtAngle(dd))
// Output:
// 1991 August 7.23797
// 1991 August 7 at 5ʰ42ᵐ41ˢ TD
// 1991 August 7 at 5ʰ41ᵐ43ˢ UT
// Δδ = 2°8′22″
}