func ExampleMeanAnomaly() {
// Example 25.a, p. 165.
T := base.J2000Century(julian.CalendarGregorianToJD(1992, 10, 13))
fmt.Printf("%.5f\n", solar.MeanAnomaly(T)*180/math.Pi)
// Output:
// -2241.00603
}
// 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())
}
// 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)
}