Exemple #1
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func ExampleEccentricity() {
	// Example 25.a, p. 165.
	T := base.J2000Century(julian.CalendarGregorianToJD(1992, 10, 13))
	fmt.Printf("%.9f\n", solar.Eccentricity(T))
	// Output:
	// 0.016711668
}
Exemple #2
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// EclipticAberration returns corrections due to aberration for ecliptic
// coordinates of an object.
func EclipticAberration(λ, β, jd float64) (Δλ, Δβ float64) {
	T := base.J2000Century(jd)
	s, _ := solar.True(T)
	e := solar.Eccentricity(T)
	π := perihelion(T)
	sβ, cβ := math.Sincos(β)
	ssλ, csλ := math.Sincos(s - λ)
	sπλ, cπλ := math.Sincos(π - λ)
	// (23.2) p. 151
	Δλ = κ * (e*cπλ - csλ) / cβ
	Δβ = -κ * sβ * (ssλ - e*sπλ)
	return
}
Exemple #3
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// EclipticAberration returns corrections due to aberration for ecliptic
// coordinates of an object.
func EclipticAberration(λ, β unit.Angle, jd float64) (Δλ, Δβ unit.Angle) {
	T := base.J2000Century(jd)
	s, _ := solar.True(T)
	e := solar.Eccentricity(T)
	π := perihelion(T)
	sβ, cβ := β.Sincos()
	ssλ, csλ := (s - λ).Sincos()
	sπλ, cπλ := (π - λ).Sincos()
	// (23.2) p. 151
	Δλ = κ.Mul((e*cπλ - csλ) / cβ)
	Δβ = -κ.Mul(sβ * (ssλ - e*sπλ))
	return
}
Exemple #4
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// ESmart computes the "equation of time" for the given JDE.
//
// Result is equation of time as an hour angle.
//
// Result is less accurate that E() but the function has the advantage
// of not requiring the V87Planet object.
func ESmart(jde float64) unit.HourAngle {
	ε := nutation.MeanObliquity(jde)
	t := ε.Mul(.5).Tan()
	y := t * t
	T := base.J2000Century(jde)
	L0 := l0(T * .1)
	e := solar.Eccentricity(T)
	M := solar.MeanAnomaly(T)
	s2L0, c2L0 := L0.Mul(2).Sincos()
	sM := M.Sin()
	// (28.3) p. 185, with double angle identity
	return unit.HourAngle(y*s2L0 - 2*e*sM + 4*e*y*sM*c2L0 -
		y*y*s2L0*c2L0 - 1.25*e*e*M.Mul(2).Sin())
}
Exemple #5
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// ESmart computes the "equation of time" for the given JDE.
//
// Result is equation of time as an hour angle in radians.
//
// Result is less accurate that E() but the function has the advantage
// of not requiring the V87Planet object.
func ESmart(jde float64) float64 {
	ε := nutation.MeanObliquity(jde)
	t := math.Tan(ε * .5)
	y := t * t
	T := base.J2000Century(jde)
	L0 := l0(T * .1)
	e := solar.Eccentricity(T)
	M := solar.MeanAnomaly(T)
	s2L0, c2L0 := math.Sincos(2 * L0)
	sM := math.Sin(M)
	// (28.3) p. 185
	return y*s2L0 - 2*e*sM + 4*e*y*sM*c2L0 -
		y*y*s2L0*c2L0 - 1.25*e*e*math.Sin(2*M)
}
Exemple #6
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// Aberration returns corrections due to aberration for equatorial
// coordinates of an object.
func Aberration(α, δ, jd float64) (Δα2, Δδ2 float64) {
	ε := nutation.MeanObliquity(jd)
	T := base.J2000Century(jd)
	s, _ := solar.True(T)
	e := solar.Eccentricity(T)
	π := perihelion(T)
	sα, cα := math.Sincos(α)
	sδ, cδ := math.Sincos(δ)
	ss, cs := math.Sincos(s)
	sπ, cπ := math.Sincos(π)
	cε := math.Cos(ε)
	tε := math.Tan(ε)
	q1 := cα * cε
	// (23.3) p. 152
	Δα2 = κ * (e*(q1*cπ+sα*sπ) - (q1*cs + sα*ss)) / cδ
	q2 := cε * (tε*cδ - sα*sδ)
	q3 := cα * sδ
	Δδ2 = κ * (e*(cπ*q2+sπ*q3) - (cs*q2 + ss*q3))
	return
}
Exemple #7
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// Aberration returns corrections due to aberration for equatorial
// coordinates of an object.
func Aberration(α unit.RA, δ unit.Angle, jd float64) (Δα2 unit.HourAngle, Δδ2 unit.Angle) {
	ε := nutation.MeanObliquity(jd)
	T := base.J2000Century(jd)
	s, _ := solar.True(T)
	e := solar.Eccentricity(T)
	π := perihelion(T)
	sα, cα := α.Sincos()
	sδ, cδ := δ.Sincos()
	ss, cs := s.Sincos()
	sπ, cπ := π.Sincos()
	cε := ε.Cos()
	tε := ε.Tan()
	q1 := cα * cε
	// (23.3) p. 152
	Δα2 = unit.HourAngle(κ.Rad() * (e*(q1*cπ+sα*sπ) - (q1*cs + sα*ss)) / cδ)
	q2 := cε * (tε*cδ - sα*sδ)
	q3 := cα * sδ
	Δδ2 = κ.Mul(e*(cπ*q2+sπ*q3) - (cs*q2 + ss*q3))
	return
}