コード例 #1
0
ファイル: rise.go プロジェクト: soniakeys/meeus
// Times computes UT rise, transit and set times for a celestial object on
// a day of interest.
//
// The function argurments do not actually include the day, but do include
// a number of values computed from the day.
//
//	p is geographic coordinates of observer.
//	ΔT is delta T.
//	h0 is "standard altitude" of the body.
//	Th0 is apparent sidereal time at 0h UT at Greenwich.
//	α3, δ3 are slices of three right ascensions and declinations.
//
// h0 unit is radians.
//
// Th0 must be the time on the day of interest, in seconds.
// See sidereal.Apparent0UT.
//
// α3, δ3 must be values at 0h dynamical time for the day before, the day of,
// and the day after the day of interest.  Units are radians.
//
// Result units are seconds of day and are in the range [0,86400).
func Times(p globe.Coord, ΔT unit.Time, h0 unit.Angle, Th0 unit.Time, α3 []unit.RA, δ3 []unit.Angle) (tRise, tTransit, tSet unit.Time, err error) {
	tRise, tTransit, tSet, err = ApproxTimes(p, h0, Th0, α3[1], δ3[1])
	if err != nil {
		return
	}
	αf := make([]float64, 3)
	for i, α := range α3 {
		αf[i] = α.Rad()
	}
	δf := make([]float64, 3)
	for i, δ := range δ3 {
		δf[i] = δ.Rad()
	}
	var d3α, d3δ *interp.Len3
	d3α, err = interp.NewLen3(-86400, 86400, αf)
	if err != nil {
		return
	}
	d3δ, err = interp.NewLen3(-86400, 86400, δf)
	if err != nil {
		return
	}
	// adjust tTransit
	{
		th0 := (Th0 + tTransit.Mul(360.985647/360)).Mod1()
		α := d3α.InterpolateX((tTransit + ΔT).Sec())
		// local hour angle as Time
		H := th0 - unit.TimeFromRad(p.Lon.Rad()+α)
		tTransit -= H
	}
	// adjust tRise, tSet
	sLat, cLat := p.Lat.Sincos()
	adjustRS := func(m unit.Time) (unit.Time, error) {
		th0 := (Th0 + m.Mul(360.985647/360)).Mod1()
		ut := (m + ΔT).Sec()
		α := d3α.InterpolateX(ut)
		δ := d3δ.InterpolateX(ut)
		Hrad := th0.Rad() - p.Lon.Rad() - α
		sδ, cδ := math.Sincos(δ)
		sH, cH := math.Sincos(Hrad)
		h := math.Asin(sLat*sδ + cLat*cδ*cH)
		md := (unit.TimeFromRad(h) - h0.Time()).Div(cδ * cLat * sH)
		return m + md, nil
	}
	tRise, err = adjustRS(tRise)
	if err != nil {
		return
	}
	tSet, err = adjustRS(tSet)
	return
}