Exemple #1
0
func ExamplePolyBefore948() {
	// Example 10.b, p. 80.
	ΔT := deltat.PolyBefore948(333.1)
	UT := unit.TimeFromHour(6)
	TD := UT + ΔT
	fmt.Printf("%+.0f seconds\n", ΔT)
	fmt.Printf("333 February 6 at %m TD", sexa.FmtTime(TD))
	// Output:
	// +6146 seconds
	// 333 February 6 at 7ʰ42ᵐ TD
}
Exemple #2
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// Lunar computes quantities related to lunar eclipses.
//
// Argument year is a decimal year specifying a date.
//
// eclipseType will be None, Penumbral, Umbral, or Total.
// If None, none of the other return values may be meaningful.
//
// jmax is the jde when the center of the eclipse shadow is closest to the
// Moon center, in a plane through the center of the Moon.
//
// γ is the distance from the eclipse shadow center to the moon center
// at time jmax.
//
// σ is the radius of the umbral cone in the plane of the Moon.
//
// ρ is the radius of the penumbral cone.
//
// mag is eclipse magnitude.
//
// sd- return values are semidurations of the phases of the eclipse.
//
// γ, σ, and ρ are in units of equatorial Earth radii.
func Lunar(year float64) (eclipseType int, jmax, γ, ρ, σ, mag float64, sdTotal, sdPartial, sdPenumbral unit.Time) {
	var e bool
	var u, Mʹ float64
	e, jmax, γ, u, Mʹ = g(snap(year, .5),
		moonphase.MeanFull(year), -.4065, .1727)
	if !e {
		return // no eclipse
	}
	ρ = 1.2848 + u
	σ = .7403 - u
	aγ := math.Abs(γ)
	mag = (1.0128 - u - aγ) / .545 // (54.3) p. 382
	switch {
	case mag > 1:
		eclipseType = Total
	case mag > 0:
		eclipseType = Umbral
	default:
		mag = (1.5573 + u - aγ) / .545 // (54.4) p. 382
		if mag < 0 {
			return // no eclipse
		}
		eclipseType = Penumbral
	}
	p := 1.0128 - u
	t := .4678 - u
	n := .5458 + .04*math.Cos(Mʹ)
	γ2 := γ * γ
	switch eclipseType {
	case Total:
		sdTotal = unit.TimeFromHour(math.Sqrt(t*t-γ2) / n)
		fallthrough
	case Umbral:
		sdPartial = unit.TimeFromHour(math.Sqrt(p*p-γ2) / n)
		fallthrough
	default:
		h := 1.5573 + u
		sdPenumbral = unit.TimeFromHour(math.Sqrt(h*h-γ2) / n)
	}
	return
}
Exemple #3
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func ExampleEclipticAtHorizon() {
	ε := unit.AngleFromDeg(23.44)
	φ := unit.AngleFromDeg(51)
	θ := unit.TimeFromHour(5)
	λ1, λ2, I := parallactic.EclipticAtHorizon(ε, φ, θ)
	fmt.Println(sexa.FmtAngle(λ1))
	fmt.Println(sexa.FmtAngle(λ2))
	fmt.Println(sexa.FmtAngle(I))
	// Output:
	// 169°21′30″
	// 349°21′30″
	// 61°53′14″
}