// mn as separate function for testing purposes
func mn(epochFrom, epochTo float64) (m, nα unit.HourAngle, nδ unit.Angle) {
T := (epochTo - epochFrom) * .01
m = unit.HourAngleFromSec(3.07496 + 0.00186*T)
nα = unit.HourAngleFromSec(1.33621 - 0.00057*T)
nδ = unit.AngleFromSec(20.0431 - 0.0085*T)
return
}
// Exercise, p. 136.
func TestPosition(t *testing.T) {
eqFrom := &coord.Equatorial{
unit.NewRA(2, 31, 48.704),
unit.NewAngle(' ', 89, 15, 50.72),
}
eqTo := &coord.Equatorial{}
mα := unit.HourAngleFromSec(0.19877)
mδ := unit.AngleFromSec(-0.0152)
for _, tc := range []struct {
α, δ string
jde float64
}{
{"1ʰ22ᵐ33.90ˢ", "88°46′26.18″", base.BesselianYearToJDE(1900)},
{"3ʰ48ᵐ16.43ˢ", "89°27′15.38″", base.JulianYearToJDE(2050)},
{"5ʰ53ᵐ29.17ˢ", "89°32′22.18″", base.JulianYearToJDE(2100)},
} {
epochTo := base.JDEToJulianYear(tc.jde)
precess.Position(eqFrom, eqTo, 2000.0, epochTo, mα, mδ)
αStr := fmt.Sprintf("%.2s", sexa.FmtRA(eqTo.RA))
δStr := fmt.Sprintf("%.2s", sexa.FmtAngle(eqTo.Dec))
if αStr != tc.α {
t.Fatal("got:", αStr, "want:", tc.α)
}
if δStr != tc.δ {
t.Fatal(δStr)
}
}
}
func ExampleProperMotion3D() {
// Example 21.d, p. 141.
eqFrom := &coord.Equatorial{
RA: unit.NewRA(6, 45, 8.871),
Dec: unit.NewAngle('-', 16, 42, 57.99),
}
mra := unit.HourAngleFromSec(-0.03847)
mdec := unit.AngleFromSec(-1.2053)
r := 2.64 // given in correct unit
mr := -7.6 / 977792 // magic conversion factor
eqTo := &coord.Equatorial{}
fmt.Printf("Δr = %.9f, Δα = %.10f, Δδ = %.10f\n", mr, mra, mdec)
for _, epoch := range []float64{1000, 0, -1000, -2000, -10000} {
precess.ProperMotion3D(eqFrom, eqTo, 2000, epoch, r, mr, mra, mdec)
fmt.Printf("%8.1f %0.2d %0.1d\n", epoch,
sexa.FmtRA(eqTo.RA), sexa.FmtAngle(eqTo.Dec))
}
// Output:
// Δr = -0.000007773, Δα = -0.0000027976, Δδ = -0.0000058435
// 1000.0 6ʰ45ᵐ47ˢ.16 -16°22′56″.0
// 0.0 6ʰ46ᵐ25ˢ.09 -16°03′00″.8
// -1000.0 6ʰ47ᵐ02ˢ.67 -15°43′12″.3
// -2000.0 6ʰ47ᵐ39ˢ.91 -15°23′30″.6
// -10000.0 6ʰ52ᵐ25ˢ.72 -12°50′06″.7
}
func TestPrecessor_Precess(t *testing.T) {
// Exercise, p. 136.
eqFrom := &coord.Equatorial{
RA: unit.NewRA(2, 31, 48.704),
Dec: unit.NewAngle(' ', 89, 15, 50.72),
}
mα := unit.HourAngleFromSec(.19877)
mδ := unit.AngleFromSec(-.0152)
epochs := []float64{
base.JDEToJulianYear(base.B1900),
2050,
2100,
}
answer := []string{
"α = 1ʰ22ᵐ33ˢ.90 δ = +88°46′26″.18",
"α = 3ʰ48ᵐ16ˢ.43 δ = +89°27′15″.38",
"α = 5ʰ53ᵐ29ˢ.17 δ = +89°32′22″.18",
}
eqTo := &coord.Equatorial{}
for i, epochTo := range epochs {
precess.Position(eqFrom, eqTo, 2000, epochTo, mα, mδ)
if answer[i] != fmt.Sprintf("α = %0.2d δ = %+0.2d",
sexa.FmtRA(eqTo.RA), sexa.FmtAngle(eqTo.Dec)) {
t.Fatal(i)
}
}
}
func ExamplePositionRonVondrak() {
// Example 23.b, p. 156
jd := julian.CalendarGregorianToJD(2028, 11, 13.19)
eq := &coord.Equatorial{
RA: unit.NewRA(2, 44, 11.986),
Dec: unit.NewAngle(' ', 49, 13, 42.48),
}
apparent.PositionRonVondrak(eq, eq, base.JDEToJulianYear(jd),
unit.HourAngleFromSec(.03425),
unit.AngleFromSec(-.0895))
fmt.Printf("α = %0.3d\n", sexa.FmtRA(eq.RA))
fmt.Printf("δ = %0.2d\n", sexa.FmtAngle(eq.Dec))
// Output:
// α = 2ʰ46ᵐ14ˢ.392
// δ = 49°21′07″.45
}
func ExampleApproxPosition() {
// Example 21.a, p. 132.
eq := &coord.Equatorial{
unit.NewRA(10, 8, 22.3),
unit.NewAngle(' ', 11, 58, 2),
}
epochFrom := 2000.0
epochTo := 1978.0
mα := unit.HourAngleFromSec(-0.0169)
mδ := unit.AngleFromSec(0.006)
precess.ApproxPosition(eq, eq, epochFrom, epochTo, mα, mδ)
fmt.Printf("%0.1d\n", sexa.FmtRA(eq.RA))
fmt.Printf("%+0d\n", sexa.FmtAngle(eq.Dec))
// Output:
// 10ʰ07ᵐ12ˢ.1
// +12°04′32″
}
func ExamplePosition() {
// Example 21.b, p. 135.
eq := &coord.Equatorial{
unit.NewRA(2, 44, 11.986),
unit.NewAngle(' ', 49, 13, 42.48),
}
epochFrom := 2000.0
jdTo := julian.CalendarGregorianToJD(2028, 11, 13.19)
epochTo := base.JDEToJulianYear(jdTo)
precess.Position(eq, eq, epochFrom, epochTo,
unit.HourAngleFromSec(0.03425),
unit.AngleFromSec(-0.0895))
fmt.Printf("%0.3d\n", sexa.FmtRA(eq.RA))
fmt.Printf("%+0.2d\n", sexa.FmtAngle(eq.Dec))
// Output:
// 2ʰ46ᵐ11ˢ.331
// +49°20′54″.54
}