225 lines
6.4 KiB
Go
225 lines
6.4 KiB
Go
package basic
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import (
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. "b612.me/astro/tools"
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"math"
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)
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// StarHeight 星体的高度角
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// 传入 jde时间、瞬时赤经、瞬时赤纬、经度、纬度、时区，jde时间应为时区时间
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// 返回高度角，单位为度
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func StarHeight(jde, ra, dec, lon, lat, timezone float64) float64 {
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// 转换为世界时
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utcJde := jde - timezone/24.0
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// 计算视恒星时
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st := Limit360(ApparentSiderealTime(utcJde)*15 + lon)
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// 计算时角
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H := Limit360(st - ra)
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// 高度角、时角与天球座标三角转换公式
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// sin(h)=sin(lat)*sin(dec)+cos(dec)*cos(lat)*cos(H)
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sinHeight := Sin(lat)*Sin(dec) + Cos(dec)*Cos(lat)*Cos(H)
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return ArcSin(sinHeight)
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}
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// StarAzimuth 星体的方位角
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// 传入 jde时间、瞬时赤经、瞬时赤纬、经度、纬度、时区，jde时间应为时区时间
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// 返回方位角，单位为度，正北为0，度数顺时针增加，取值范围[0-360)
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func StarAzimuth(jde, ra, dec, lon, lat, timezone float64) float64 {
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// 转换为世界时
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utcJde := jde - timezone/24.0
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// 计算视恒星时
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st := Limit360(ApparentSiderealTime(utcJde)*15 + lon)
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// 计算时角
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H := Limit360(st - ra)
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// 三角转换公式
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tanAzimuth := Sin(H) / (Cos(H)*Sin(lat) - Tan(dec)*Cos(lat))
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Azimuth := ArcTan(tanAzimuth)
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if Azimuth < 0 {
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if H/15 < 12 {
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return Azimuth + 360
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}
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return Azimuth + 180
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}
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if H/15 < 12 {
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return Azimuth + 180
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}
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return Azimuth
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}
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// StarHourAngle 星体的时角
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// 传入 jde时间、瞬时赤经、瞬时赤纬、经度、时区，jde时间应为时区时间
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// 返回时角
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func StarHourAngle(jde, ra, lon, timezone float64) float64 {
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// 转换为世界时
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utcJde := jde - timezone/24.0
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// 计算视恒星时
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st := Limit360(ApparentSiderealTime(utcJde)*15 + lon)
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// 计算时角
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return Limit360(st - ra)
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}
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// MeanSiderealTime 平恒星时
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func MeanSiderealTime(JD float64) float64 {
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return MeanSiderealTime2006(JD)
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}
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// ApparentSiderealTime 视恒星时，计算章动
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func ApparentSiderealTime(JD float64) float64 {
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return ApparentSiderealTime2006(JD)
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}
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// MeanSiderealTime1982 不含章动下的恒星时
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func MeanSiderealTime1982(JD float64) float64 {
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T := (JD - 2451545) / 36525
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return (Limit360(280.46061837+360.98564736629*(JD-2451545.0)+0.000387933*T*T-T*T*T/38710000) / 15)
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}
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// ApparentSiderealTime1982 视恒星时，计算章动
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func ApparentSiderealTime1982(JD float64) float64 {
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tmp := MeanSiderealTime1982(JD)
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return tmp + Nutation2000Bi(JD)*Cos(Sita(JD))/15
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}
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// EarthRotationAngle 计算地球自转角 (ERA)
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// jd_ut1: UT1 时间的儒略日
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// 返回值: 地球自转角 (弧度)
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func EarthRotationAngle(jd_ut1 float64) float64 {
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t := jd_ut1 - 2451545.0
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frac := math.Mod(jd_ut1, 1.0)
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era := math.Mod(math.Pi*2*(0.7790572732640+0.00273781191135448*t+frac), math.Pi*2)
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if era < 0 {
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era += math.Pi * 2
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}
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return era
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}
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// MeanSiderealTime2006 计算格林尼治平恒星时 (GMST)
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// jd_ut1: UT1 时间的儒略日
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// jd_tt: TT 时间的儒略日
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// 返回值: 格林尼治平恒星时 (弧度)
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func MeanSiderealTime2006(jd_ut1 float64) float64 {
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jd_tt := TD2UT(jd_ut1, true)
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t := (jd_tt - 2451545.0) / 36525.0
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era := EarthRotationAngle(jd_ut1)
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// 公式 2.12
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gmst := math.Mod(era+(0.014506+4612.15739966*t+1.39667721*t*t+
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-0.00009344*t*t*t+0.00001882*t*t*t*t)/60/60*math.Pi/180, math.Pi*2)
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if gmst < 0 {
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gmst += math.Pi * 2
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}
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return gmst * deg / 15
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}
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// ApparentSiderealTime2006 视恒星时，计算章动
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func ApparentSiderealTime2006(JD float64) float64 {
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tmp := MeanSiderealTime2006(JD)
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return tmp + Nutation2000Bi(JD)*Cos(Sita(JD))/15
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}
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func StarAngle(RA, DEC, JD, Lon, Lat, TZ float64) float64 {
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//JD=JD-8/24+TZ/24;
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calcjd := JD - TZ/24
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st := Limit360(ApparentSiderealTime(calcjd)*15 + Lon)
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H := Limit360(st - RA)
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tmp2 := Sin(H) / (Cos(H)*Sin(Lat) - Tan(DEC)*Cos(Lat))
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Angle := ArcTan(tmp2)
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if Angle < 0 {
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if H/15 < 12 {
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return Angle + 360
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} else {
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return Angle + 180
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}
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} else {
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if H/15 < 12 {
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return Angle + 180
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} else {
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return Angle
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}
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}
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}
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func StarRiseTime(jde, ra, dec, lon, lat, height, timezone float64, aero bool) float64 {
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return StarRiseDownTime(jde, ra, dec, lon, lat, height, timezone, aero, true)
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}
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func StarDownTime(jde, ra, dec, lon, lat, height, timezone float64, aero bool) float64 {
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return StarRiseDownTime(jde, ra, dec, lon, lat, height, timezone, aero, false)
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}
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func StarRiseDownTime(jde, ra, dec, lon, lat, height, timezone float64, aero, isRise bool) float64 {
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//jde 世界时，非力学时，当地时区 0时，无需转换力学时
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//ra,dec 瞬时天球座标，非J2000等时间天球坐标
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jde = math.Floor(jde) + 0.5
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var An float64 = 0
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if aero {
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An = -0.566667
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}
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An = An - HeightDegreeByLat(height, lat)
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sct := StarCulminationTime(jde, ra, lon, timezone)
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tmp := (Sin(An) - Sin(dec)*Sin(lat)) / (Cos(dec) * Cos(lat))
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if math.Abs(tmp) > 1 {
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if StarHeight(sct, ra, dec, lon, lat, timezone) < 0 {
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return -2 //极夜
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} else {
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return -1 //极昼
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}
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}
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var JD1 float64
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if isRise {
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JD1 = sct - ArcCos(tmp)/15.0/24.0
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} else {
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JD1 = sct + ArcCos(tmp)/15.0/24.0
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}
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for {
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JD0 := JD1
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stDegree := StarHeight(JD0, ra, dec, lon, lat, timezone) - An
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stDegreep := (StarHeight(JD0+0.000005, ra, dec, lon, lat, timezone) - StarHeight(JD0-0.000005, ra, dec, lon, lat, timezone)) / 0.00001
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JD1 = JD0 - stDegree/stDegreep
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if math.Abs(JD1-JD0) <= 0.00001 {
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break
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}
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}
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return JD1
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}
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func StarCulminationTime(jde, ra, lon, timezone float64) float64 {
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//jde 世界时，非力学时，当地时区 0时，无需转换力学时
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//ra,dec 瞬时天球座标，非J2000等时间天球坐标
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jde = math.Floor(jde) + 0.5
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JD1 := jde + Limit360(360-StarHourAngle(jde, ra, lon, timezone))/15.0/24.0*0.99726851851851851851
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limitStarHA := func(jde, ra, lon, timezone float64) float64 {
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ha := StarHourAngle(jde, ra, lon, timezone)
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if ha < 180 {
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ha += 360
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}
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return ha
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}
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for {
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JD0 := JD1
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stDegree := limitStarHA(JD0, ra, lon, timezone) - 360
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stDegreep := (limitStarHA(JD0+0.000005, ra, lon, timezone) - limitStarHA(JD0-0.000005, ra, lon, timezone)) / 0.00001
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JD1 = JD0 - stDegree/stDegreep
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if math.Abs(JD1-JD0) <= 0.00001 {
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break
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}
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}
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return JD1
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}
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func StarAngularSeparation(ra1, dec1, ra2, dec2 float64) float64 {
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//cos(d)=sinδ1 sinδ2 + cosδ1 cosδ2 cos(α1-α2)
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d := Sin(dec1)*Sin(dec2) + Cos(dec1)*Cos(dec2)*Cos(ra1-ra2)
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if math.Abs(d) >= 0.999999997 {
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//d = √(Δα*cosδ)2+(Δδ)2
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tmp1 := ((ra1 - ra2) * Cos((dec1+dec2)/2))
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tmp2 := (dec1 - dec2)
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return math.Sqrt(tmp1*tmp1 + tmp2*tmp2)
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}
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return ArcCos(d)
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}
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