feat: 完善时标与天象几何计算并扩展输出接口
- 新增时标、ΔT 模型、质心时间与 UT1 支持 - 改进日月食、月掩、行星事件及路径边界计算 - 完善恒星三维自行与动态距离传播 - 扩展 SVG、GeoJSON、KML 输出与底层距离换算工具 - 整理中英文手册、示例资源及回归测试
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+79
-17
@@ -273,7 +273,7 @@ func starOccultationMinimizeValue(left, right float64, value func(float64) float
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func starOccultationGeocentricSeparationArcsec(tt float64, star StarCoordinate) float64 {
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moonRA, moonDec := HMoonGeocentricApparentRaDecN(tt, -1)
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starRA, starDec := starApparentRaDecGeocentric(tt, star)
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starRA, starDec, _ := starApparentRaDecDistanceGeocentric(tt, star)
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return angularSeparationDegrees(moonRA, moonDec, starRA, starDec) * 3600
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}
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@@ -389,45 +389,107 @@ func starMoonPositionAt(tt float64, star StarCoordinate, observer Observer) star
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func moonTopocentricApparentRaDec(tt float64, observer Observer, n int) (float64, float64) {
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ra, dec := HMoonGeocentricApparentRaDecN(tt, n)
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ut := TD2UT(tt, false)
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ut := TT2UTC(tt)
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distanceAU := HMoonAwayN(tt, n) / 149597870.7
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ra, dec = TopocentricRaDec(ra, dec, observer.Latitude, observer.Longitude, ut, distanceAU, observer.Height)
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return normalizeRA(ra), dec
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}
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func starApparentRaDec(tt float64, star StarCoordinate, observer Observer) (float64, float64) {
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ra, dec := starApparentRaDecGeocentric(tt, star)
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if star.ParallaxMas > 0 {
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// 1 秒差距处 1 角秒对应 206264.806 AU。
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// One arcsecond at 1 pc corresponds to 206264.806 AU.
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distanceAU := 206264806.247 / star.ParallaxMas
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ra, dec = TopocentricRaDec(ra, dec, observer.Latitude, observer.Longitude, TD2UT(tt, false), distanceAU, observer.Height)
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ra, dec, distanceAU := starApparentRaDecDistanceGeocentric(tt, star)
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if distanceAU > 0 {
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ra, dec = TopocentricRaDec(ra, dec, observer.Latitude, observer.Longitude, TT2UTC(tt), distanceAU, observer.Height)
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ra = normalizeRA(ra)
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}
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return ra, dec
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}
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func starApparentRaDecGeocentric(tt float64, star StarCoordinate) (float64, float64) {
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ra, dec, _ := starApparentRaDecDistanceGeocentric(tt, star)
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return ra, dec
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}
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// starApparentRaDecDistanceGeocentric 同时给出视位置与推进后的距离（天文单位，0 表示距离未知）。
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func starApparentRaDecDistanceGeocentric(tt float64, star StarCoordinate) (float64, float64, float64) {
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epochJD := occultationTimeToTT(star.Epoch)
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years := (tt - epochJD) / 365.25
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parallaxMas := star.parallaxMas()
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ra := star.RA
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dec := star.Dec
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precessionEpoch := 2451545.0
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if star.Frame == CoordinateFrameICRS {
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ra, dec = starICRSToMeanJ2000RaDec(ra, dec)
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} else if star.Frame == CoordinateFrameApparentOfDate {
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ra, dec = starApparentToMeanRaDec(epochJD, ra, dec, star.ParallaxMas)
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ra, dec = starApparentToMeanRaDec(epochJD, ra, dec, parallaxMas)
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precessionEpoch = epochJD
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}
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epochDistanceAU := starEpochDistanceAU(parallaxMas)
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ra, dec, distanceAU := starProperMotionRaDec(tt, star, ra, dec, epochDistanceAU)
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ra, dec = Precess(ra, dec, precessionEpoch, tt)
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ra, dec = starMeanToApparentRaDec(tt, ra, dec, parallaxMasAtDistance(parallaxMas, distanceAU))
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return ra, dec, distanceAU
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}
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// starEpochDistanceAU 由历元视差给出距离，非正表示距离未知。
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func starEpochDistanceAU(parallaxMas float64) float64 {
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if parallaxMas <= 0 {
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return 0
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}
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return 206264806.247 / parallaxMas
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}
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// starPropagatedPositionAU 把历元位置矢量按三维匀速直线运动推进一个历元差。
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// 切向速度取自行乘历元距离，视向分量取径向速度；返回推进后的矢量，其模长即当日距离。
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func starPropagatedPositionAU(star StarCoordinate, ra, dec, epochDistanceAU, years float64) ([3]float64, float64) {
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if epochDistanceAU <= 0 {
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return [3]float64{}, 0
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}
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raRad := ra * math.Pi / 180
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decRad := dec * math.Pi / 180
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cosDec, sinDec := math.Cos(decRad), math.Sin(decRad)
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cosRA, sinRA := math.Cos(raRad), math.Sin(raRad)
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pmRA := star.ProperMotionRACosDecMasPerYear / 1000 * math.Pi / (180 * 3600) * epochDistanceAU
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pmDec := star.ProperMotionDecMasPerYear / 1000 * math.Pi / (180 * 3600) * epochDistanceAU
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radial := star.RadialVelocityKmPerSecond * 365.25 * 86400 / 149597870.7
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position := [3]float64{
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epochDistanceAU*cosDec*cosRA + years*(pmDec*(-sinDec*cosRA)-pmRA*sinRA+radial*cosDec*cosRA),
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epochDistanceAU*cosDec*sinRA + years*(pmDec*(-sinDec*sinRA)+pmRA*cosRA+radial*cosDec*sinRA),
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epochDistanceAU*sinDec + years*(pmDec*cosDec+radial*sinDec),
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}
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norm := math.Sqrt(position[0]*position[0] + position[1]*position[1] + position[2]*position[2])
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return position, norm
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}
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// parallaxMasAtDistance 把推进后的距离折回周年视差，视差修正必须跟着距离一起变。
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func parallaxMasAtDistance(parallaxMas, distanceAU float64) float64 {
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if parallaxMas <= 0 || distanceAU <= 0 {
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return 0
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}
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return 206264806.247 / distanceAU
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}
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// starProperMotionRaDec 把历元输入坐标推进到 tt，并给出推进后的距离。
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// 距离已知走三维、否则只推进两个角分量（此时距离返回 0）。
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func starProperMotionRaDec(tt float64, star StarCoordinate, ra, dec, epochDistanceAU float64) (float64, float64, float64) {
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years := (tt - occultationTimeToTT(star.Epoch)) / 365.25
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if epochDistanceAU > 0 {
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return starProperMotionRaDec3D(ra, dec, years, epochDistanceAU, star)
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}
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cosDec := math.Cos(dec * math.Pi / 180)
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if math.Abs(cosDec) > 1e-12 {
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ra += years * star.ProperMotionRACosDecMasPerYear / (3600000.0 * cosDec)
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}
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dec += years * star.ProperMotionDecMasPerYear / 3600000.0
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dec = math.Max(-90, math.Min(90, dec))
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return ra, math.Max(-90, math.Min(90, dec)), 0
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}
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ra, dec = Precess(ra, dec, precessionEpoch, tt)
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return starMeanToApparentRaDec(tt, ra, dec, star.ParallaxMas)
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// starProperMotionRaDec3D 按三维匀速直线运动推进：赤经赤纬只是位置矢量的方向。
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func starProperMotionRaDec3D(ra, dec, years, epochDistanceAU float64, star StarCoordinate) (float64, float64, float64) {
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position, norm := starPropagatedPositionAU(star, ra, dec, epochDistanceAU, years)
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outRA := math.Atan2(position[1], position[0]) * 180 / math.Pi
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if outRA < 0 {
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outRA += 360
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}
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return outRA, math.Asin(position[2]/norm) * 180 / math.Pi, norm
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}
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func starICRSToMeanJ2000RaDec(ra, dec float64) (float64, float64) {
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@@ -628,7 +690,7 @@ func occultationPositionAngle(moonRA, moonDec, starRA, starDec float64) float64
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func occultationAltitude(tt float64, observer Observer, ra, dec float64) float64 {
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return occultationAltitudeWithSidereal(
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ApparentSiderealTime(TD2UT(tt, false))*15, observer, ra, dec,
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ApparentSiderealTime(TT2UT1(tt))*15, observer, ra, dec,
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)
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}
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@@ -641,7 +703,7 @@ func occultationAltitudeWithSidereal(siderealDegrees float64, observer Observer,
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}
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func occultationAzimuth(tt float64, observer Observer, ra, dec float64) float64 {
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hourAngle := signedAngleDifference(ApparentSiderealTime(TD2UT(tt, false))*15+observer.Longitude, ra) * math.Pi / 180
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hourAngle := signedAngleDifference(ApparentSiderealTime(TT2UT1(tt))*15+observer.Longitude, ra) * math.Pi / 180
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lat := observer.Latitude * math.Pi / 180
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declination := dec * math.Pi / 180
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y := math.Sin(hourAngle)
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@@ -666,12 +728,12 @@ func normalizeRA(ra float64) float64 {
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}
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func occultationTimeToTT(value time.Time) float64 {
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return TD2UT(Date2JDE(value.UTC()), true)
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return UTC2TT(Date2JD(value.UTC()))
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}
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func occultationTTToLocation(tt float64, location *time.Location) time.Time {
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if location == nil {
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location = time.UTC
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}
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return JDE2DateByZone(TD2UT(tt, false), location, false)
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return JD2DateByZone(TT2UTC(tt), location, false)
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}
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