feat: 新增月掩与日月食地理绘图并提升观测计算精度

- 新增月掩恒星和行星：支持搜索、掩甚点、全球掩带及固定地点轨迹计算
- 支持恒星星表坐标转换、有限盘面行星接触事件和月掩 SVG 输出
- 新增日月食及月掩全球投影图、时间标记和 GeoJSON 地理数据接口
- 扩展日食中心线、南北界及偏食足迹采样，支持极区投影
- 修正站心时角、月出月落、月球视半径、折射和恒星自行计算
- 优化内外行星事件搜索、边界选择、极端输入处理和计算稳定性

basic/coordinate_topocentric_test.go

@@ -0,0 +1,81 @@
+package basic
+
+import (
+	"math"
+	"testing"
+	"time"
+
+	. "b612.me/astro/tools"
+)
+
+func TestTopocentricRaDecUsesUTJulianDateForSiderealTime(t *testing.T) {
+	ut := Date2JDE(time.Date(2025, 6, 5, 12, 2, 7, 700000000, time.UTC))
+	ra := 189.527817246
+	dec := -5.973400893
+	lat := 6.79657
+	lon := 121.55381
+	distanceAU := HMoonAwayN(TD2UT(ut, true), -1) / 149597870.7
+
+	gotRA, gotDec := TopocentricRaDec(ra, dec, lat, lon, ut, distanceAU, 0)
+	wantRA, wantDec := independentTopocentricRaDec(ra, dec, lat, lon, ut, distanceAU, 0)
+	if delta := angularDistanceArcsec(gotRA, gotDec, wantRA, wantDec); delta > 1e-6 {
+		t.Fatalf("TopocentricRaDec differs from independent formula by %.9f arcsec", delta)
+	}
+}
+
+func TestTopocentricRaAndDecMatchCombinedResult(t *testing.T) {
+	ut := Date2JDE(time.Date(2025, 6, 5, 12, 2, 7, 700000000, time.UTC))
+	ra := 189.527817246
+	dec := -5.973400893
+	lat := 6.79657
+	lon := 121.55381
+	distanceAU := HMoonAwayN(TD2UT(ut, true), -1) / 149597870.7
+
+	wantRA, wantDec := TopocentricRaDec(ra, dec, lat, lon, ut, distanceAU, 0)
+	if got := TopocentricRa(ra, dec, lat, lon, ut, distanceAU, 0); got != wantRA {
+		t.Fatalf("TopocentricRa = %.12f, want %.12f", got, wantRA)
+	}
+	if got := TopocentricDec(ra, dec, lat, lon, ut, distanceAU, 0); got != wantDec {
+		t.Fatalf("TopocentricDec = %.12f, want %.12f", got, wantDec)
+	}
+}
+
+func TestHMoonHeightUsesUTForTopocentricCorrection(t *testing.T) {
+	ut := Date2JDE(time.Date(2026, 4, 28, 16, 1, 30, 0, time.UTC))
+	longitude := 0.0
+	latitude := 51.4779
+	ra, dec := HMoonApparentRaDecN(ut, longitude, latitude, 0, -1)
+	hourAngle := Limit360(ApparentSiderealTime(ut)*15 + longitude - ra)
+	want := ArcSin(Sin(latitude)*Sin(dec) + Cos(dec)*Cos(latitude)*Cos(hourAngle))
+	got := HMoonHeightN(ut, longitude, latitude, 0, -1)
+	if difference := math.Abs(got - want); difference > 1e-10 {
+		t.Fatalf("HMoonHeightN differs from the UT topocentric position by %.12f degrees", difference)
+	}
+}
+
+func independentTopocentricRaDec(ra, dec, lat, lon, ut, distanceAU, height float64) (float64, float64) {
+	const (
+		equatorialRadiusKM = 6378.14
+		polarRadiusKM      = 6356.755
+	)
+	u := math.Atan(polarRadiusKM / equatorialRadiusKM * Tan(lat))
+	rhoCos := math.Cos(u) + height/6378140.0*Cos(lat)
+	rhoSin := polarRadiusKM/equatorialRadiusKM*math.Sin(u) + height/6378140.0*Sin(lat)
+	sinParallax := Sin(0.0024427777777) / distanceAU
+	hourAngle := Limit360(ApparentSiderealTime(ut)*15 + lon - ra)
+	deltaRA := math.Atan2(
+		-rhoCos*sinParallax*Sin(hourAngle),
+		Cos(dec)-rhoCos*sinParallax*Cos(hourAngle),
+	)
+	topRA := ra + deltaRA*180/math.Pi
+	topDec := math.Atan2(
+		(Sin(dec)-rhoSin*sinParallax)*math.Cos(deltaRA),
+		Cos(dec)-rhoCos*sinParallax*Cos(hourAngle),
+	) * 180 / math.Pi
+	return topRA, topDec
+}
+
+func angularDistanceArcsec(ra1, dec1, ra2, dec2 float64) float64 {
+	cosDistance := Sin(dec1)*Sin(dec2) + Cos(dec1)*Cos(dec2)*Cos(ra1-ra2)
+	return math.Acos(math.Max(-1, math.Min(1, cosDistance))) * 180 / math.Pi * 3600
+}