b612
2bf8478639
- 新增日月食中心带、偏食带、阴影足迹、等时线、食分线及升落边界计算，支持极区与混合食拓扑 - 新增日食单时刻阴影求解器、站心状态查询、批量采样和 ΔT 覆盖接口 - 重构恒星与行星月掩路径，补充有限盘面接触、站心修正、掩带宽度、极区投影及升落边界 - 扩展 SVG 与 GeoJSON 输出，支持详细面板、全球/极区/地球投影、边界闭合、时间标记和拓扑签名 - 扩展日月食候选搜索、局地搜索、沙罗序列预计算与范围外推，补充系列锚点和成员一致性校验 - 补齐古历纪年、儒略历独有闰日、多公历候选、历法改革跨日及精确日期运算接口 - 优化 ΔT、章动、恒星时、月球地平线、事件根搜索和本地星历缓存，降低重复计算开销并提升边界稳定
59 lines
2.5 KiB
Go
59 lines
2.5 KiB
Go
package basic
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import "math"
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// MoonHorizon 返回 UT 儒略日下海平面几何月球中心地平圈（月球恰好在地平线上的观测者轨迹，
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// 即月下点周围的地平圈）的 [经度, 纬度] 顶点，单位为度，不重复首点。视差与椭球口径同
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// HMoonHeight，不含折射；与 HMoonHeight(经, 纬, ..., 0) 配合时该圈上的点高度角为 0。
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// samples<=0 取 360，其余夹到 [12, 1440]。
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// MoonHorizon returns sea-level geometric Moon-centre horizon vertices in degrees for a UT Julian
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// day: the locus of observers that see the Moon exactly on the horizon. Parallax and the observer
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// ellipsoid match HMoonHeight; refraction is excluded.
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func MoonHorizon(jdUT float64, samples int) [][2]float64 {
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if !finite(jdUT) {
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return nil
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}
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if samples <= 0 {
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samples = 360
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}
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if samples < 12 {
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samples = 12
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} else if samples > 1440 {
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samples = 1440
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}
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tt := TD2UT(jdUT, true)
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ra, dec := HMoonTrueRaDec(tt)
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distanceAU := HMoonAway(tt) / angularDiameterAstronomicalUnitKM
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parallax := math.Sin(0.0024427777777*rad) / distanceAU
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longitude := (ra - ApparentSiderealTime(jdUT)*15) * rad
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latitude := dec * rad
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if !finite(parallax) || parallax <= 0 || parallax >= 1 || !finite(longitude) || !finite(latitude) {
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return nil
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}
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center := [3]float64{math.Cos(latitude) * math.Cos(longitude), math.Cos(latitude) * math.Sin(longitude), math.Sin(latitude)}
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north := [3]float64{-math.Sin(latitude) * math.Cos(longitude), -math.Sin(latitude) * math.Sin(longitude), math.Cos(latitude)}
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east := [3]float64{-math.Sin(longitude), math.Cos(longitude), 0}
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points := make([][2]float64, samples)
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for index := range points {
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bearing := 2 * math.Pi * float64(index) / float64(samples)
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radius := math.Acos(parallax)
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var point [3]float64
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for iteration := 0; iteration < 8; iteration++ {
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for axis := range point {
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point[axis] = center[axis]*math.Cos(radius) +
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(north[axis]*math.Cos(bearing)+east[axis]*math.Sin(bearing))*math.Sin(radius)
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}
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lat := math.Asin(math.Max(-1, math.Min(1, point[2]))) / rad
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// The topocentric direction is horizontal when its dot product
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// with the geodetic zenith vanishes: cos(radius)=observer/range.
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next := math.Acos(parallax * (pcosi(lat, 0)*math.Cos(lat*rad) + psini(lat, 0)*math.Sin(lat*rad)))
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if math.Abs(next-radius) < 1e-14 {
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break
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}
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radius = next
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}
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points[index] = [2]float64{math.Atan2(point[1], point[0]) / rad, math.Asin(math.Max(-1, math.Min(1, point[2]))) / rad}
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}
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return points
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}
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