astro/coord/coord_test.go

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package coord
import (
"math"
"testing"
"time"
"b612.me/astro/basic"
)
func assertClose(t *testing.T, name string, got, want, tolerance float64) {
t.Helper()
if math.Abs(got-want) > tolerance {
t.Fatalf("%s mismatch: got %.15f want %.15f", name, got, want)
}
}
func TestEclipticEquatorialWrappers(t *testing.T) {
date := time.Date(2026, 4, 27, 10, 30, 45, 0, time.FixedZone("CST", 8*3600))
jde := basic.Date2JDE(date.UTC())
lon := 139.686111
lat := 4.875278
got := EclipticToEquatorial(date, lon, lat)
wantRA, wantDec := basic.LoBoToRaDec(jde, lon, lat)
assertClose(t, "ra", got.RA, wantRA, 1e-12)
assertClose(t, "dec", got.Dec, wantDec, 1e-12)
back := EquatorialToEcliptic(date, got.RA, got.Dec)
assertClose(t, "lon", back.Lon, lon, 1e-10)
assertClose(t, "lat", back.Lat, lat, 1e-10)
}
func TestTimeAndPrecessionWrappers(t *testing.T) {
date := time.Date(2026, 4, 27, 2, 30, 45, 0, time.UTC)
to := time.Date(2050, 1, 1, 0, 0, 0, 0, time.UTC)
jde := basic.Date2JDE(date.UTC())
assertClose(t, "mean sidereal time", MeanSiderealTime(date), basic.MeanSiderealTime(jde), 1e-12)
assertClose(t, "apparent sidereal time", ApparentSiderealTime(date), basic.ApparentSiderealTime(jde), 1e-12)
assertClose(t, "obliquity", EclipticObliquity(date, true), basic.EclipticObliquity(jde, true), 1e-12)
gotLon, gotObl := Nutation2000B(date)
wantLon, wantObl := basic.Nutation2000B(jde)
assertClose(t, "nutation longitude", gotLon, wantLon, 1e-12)
assertClose(t, "nutation obliquity", gotObl, wantObl, 1e-12)
got := Precess(date, to, 101.28715533, -16.71611586)
wantRA, wantDec := basic.Precess(101.28715533, -16.71611586, jde, basic.Date2JDE(to.UTC()))
assertClose(t, "precess ra", got.RA, wantRA, 1e-12)
assertClose(t, "precess dec", got.Dec, wantDec, 1e-12)
}
func TestHorizontalAndTopocentricWrappers(t *testing.T) {
date := time.Date(2026, 4, 27, 2, 30, 45, 0, time.UTC)
jde := basic.Date2JDE(date.UTC())
ra := 101.28715533
dec := -16.71611586
observerLon := 115.0
observerLat := 40.0
hz := EquatorialToHorizontal(date, ra, dec, observerLon, observerLat)
wantAltitude := basic.StarHeight(jde, ra, dec, observerLon, observerLat, 0)
assertClose(t, "altitude", hz.Altitude, wantAltitude, 1e-12)
assertClose(t, "zenith", hz.Zenith, 90-wantAltitude, 1e-12)
assertClose(t, "azimuth", hz.Azimuth, basic.StarAzimuth(jde, ra, dec, observerLon, observerLat, 0), 1e-12)
assertClose(t, "hour angle", hz.HourAngle, basic.StarHourAngle(jde, ra, observerLon, 0), 1e-12)
assertClose(t, "hour angle func", HourAngle(date, ra, observerLon), hz.HourAngle, 1e-12)
top := TopocentricEquatorial(date, ra, dec, observerLon, observerLat, 0.00257, 53)
wantRA, wantDec := basic.TopocentricRaDec(ra, dec, observerLat, observerLon, jde, 0.00257, 53)
assertClose(t, "topocentric ra", top.RA, wantRA, 1e-12)
assertClose(t, "topocentric dec", top.Dec, wantDec, 1e-12)
ecl := TopocentricEcliptic(date, 139.686111, 4.875278, observerLon, observerLat, 0.00257, 53)
assertClose(t, "topocentric lon", ecl.Lon, basic.TopocentricLo(139.686111, 4.875278, observerLat, observerLon, jde, 0.00257, 53), 1e-12)
assertClose(t, "topocentric lat", ecl.Lat, basic.TopocentricBo(139.686111, 4.875278, observerLat, observerLon, jde, 0.00257, 53), 1e-12)
}
func TestAngularSeparationWrapper(t *testing.T) {
got := AngularSeparation(101.28715533, -16.71611586, 95.9879578, -52.6956611)
want := basic.StarAngularSeparation(101.28715533, -16.71611586, 95.9879578, -52.6956611)
assertClose(t, "angular separation", got, want, 1e-12)
}