starainrt
3ffdbe0034
- 新增日食、月食、本地可见性、中心线、半影区域、SVG 图示与沙罗周期信息 - 新增行星冲合、留、方照、物理星历、视直径、相位、亮肢角、轨道节点等计算 - 新增木星伽利略卫星位置、现象与接触事件计算 - 新增恒星星表、星座判定、自行修正与观测辅助能力 - 新增 coord、formula、orbit、sundial、lite/sun、lite/moon 等扩展包 - 完善农历年号、月相英文别名、视差角、大气质量、折射、日晷与双星计算 - 增加 NASA、JPL Horizons、IMCCE 等回归测试数据与基线测试 - 重构基础算法文件组织，补充大量公开 API 注释和语义回归测试 - 更新中文和英文 README，补充示例、精度说明、SVG 配图
130 lines
5.4 KiB
Go
130 lines
5.4 KiB
Go
// Package coord 坐标工具包 / coordinate utility package.
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//
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// 本包面向用户提供常用坐标变换、恒星时、岁差、站心和地平坐标封装。
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// 所有角度输入和输出默认使用度；恒星时输出使用小时。
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// date 按绝对时刻使用，内部会转换为 UTC 后计算。
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package coord
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import (
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"time"
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"b612.me/astro/basic"
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)
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// Ecliptic 黄道坐标 / ecliptic coordinates.
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type Ecliptic struct {
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Lon float64 // 黄经，单位度 / ecliptic longitude in degrees.
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Lat float64 // 黄纬，单位度 / ecliptic latitude in degrees.
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}
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// Equatorial 赤道坐标 / equatorial coordinates.
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type Equatorial struct {
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RA float64 // 赤经，单位度 / right ascension in degrees.
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Dec float64 // 赤纬，单位度 / declination in degrees.
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}
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// Horizontal 地平坐标 / horizontal coordinates.
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type Horizontal struct {
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Azimuth float64 // 方位角，正北为0，顺时针增加 / azimuth from north clockwise, degrees.
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Altitude float64 // 高度角，单位度 / altitude in degrees.
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Zenith float64 // 天顶距，单位度 / zenith distance in degrees.
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HourAngle float64 // 时角，单位度 / hour angle in degrees.
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}
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func jdeUTC(date time.Time) float64 {
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return basic.Date2JDE(date.UTC())
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}
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// EclipticToEquatorial 黄道坐标转赤道坐标 / converts ecliptic to equatorial coordinates.
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func EclipticToEquatorial(date time.Time, lon, lat float64) Equatorial {
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ra, dec := basic.LoBoToRaDec(jdeUTC(date), lon, lat)
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return Equatorial{RA: ra, Dec: dec}
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}
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// EquatorialToEcliptic 赤道坐标转黄道坐标 / converts equatorial to ecliptic coordinates.
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func EquatorialToEcliptic(date time.Time, ra, dec float64) Ecliptic {
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lon, lat := basic.RaDecToLoBo(jdeUTC(date), ra, dec)
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return Ecliptic{Lon: lon, Lat: lat}
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}
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// Precess 岁差修正 / precesses equatorial coordinates from one date to another.
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func Precess(from, to time.Time, ra, dec float64) Equatorial {
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nextRA, nextDec := basic.Precess(ra, dec, jdeUTC(from), jdeUTC(to))
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return Equatorial{RA: nextRA, Dec: nextDec}
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}
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// EclipticObliquity 黄赤交角 / ecliptic obliquity.
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func EclipticObliquity(date time.Time, nutation bool) float64 {
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return basic.EclipticObliquity(jdeUTC(date), nutation)
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}
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// Nutation2000B IAU 2000B 章动 / IAU 2000B nutation.
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func Nutation2000B(date time.Time) (longitude, obliquity float64) {
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return basic.Nutation2000B(jdeUTC(date))
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}
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// Nutation1980 IAU 1980 章动 / IAU 1980 nutation.
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func Nutation1980(date time.Time) (longitude, obliquity float64) {
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return basic.Nutation1980(jdeUTC(date))
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}
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// MeanSiderealTime 平恒星时，单位小时 / mean sidereal time in hours.
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func MeanSiderealTime(date time.Time) float64 {
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return basic.MeanSiderealTime(jdeUTC(date))
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}
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// ApparentSiderealTime 真恒星时，单位小时 / apparent sidereal time in hours.
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func ApparentSiderealTime(date time.Time) float64 {
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return basic.ApparentSiderealTime(jdeUTC(date))
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}
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// HourAngle 时角 / hour angle.
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//
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// ra 为瞬时赤经；observerLon 为观测者经度，东正西负。
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// ra is apparent right ascension; observerLon is east-positive longitude.
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func HourAngle(date time.Time, ra, observerLon float64) float64 {
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return basic.StarHourAngle(jdeUTC(date), ra, observerLon, 0)
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}
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// EquatorialToHorizontal 赤道坐标转地平坐标 / converts equatorial to horizontal coordinates.
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//
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// ra/dec 为瞬时赤经赤纬；observerLon/observerLat 为观测者经纬度，东正西负、北正南负。
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// ra/dec are apparent coordinates; observerLon/observerLat are east-positive and north-positive.
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func EquatorialToHorizontal(date time.Time, ra, dec, observerLon, observerLat float64) Horizontal {
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jde := jdeUTC(date)
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altitude := basic.StarHeight(jde, ra, dec, observerLon, observerLat, 0)
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return Horizontal{
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Azimuth: basic.StarAzimuth(jde, ra, dec, observerLon, observerLat, 0),
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Altitude: altitude,
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Zenith: 90 - altitude,
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HourAngle: basic.StarHourAngle(jde, ra, observerLon, 0),
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}
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}
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// TopocentricEquatorial 地心赤道坐标转站心赤道坐标 / converts geocentric to topocentric equatorial coordinates.
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//
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// distanceAU 为目标天体到地心距离，单位 AU；height 为观测者海拔，单位米。
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// distanceAU is geocentric distance in AU; height is observer elevation in meters.
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func TopocentricEquatorial(date time.Time, ra, dec, observerLon, observerLat, distanceAU, height float64) Equatorial {
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topRA, topDec := basic.TopocentricRaDec(ra, dec, observerLat, observerLon, jdeUTC(date), distanceAU, height)
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return Equatorial{RA: topRA, Dec: topDec}
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}
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// TopocentricEcliptic 地心黄道坐标转站心黄道坐标 / converts geocentric to topocentric ecliptic coordinates.
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//
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// distanceAU 为目标天体到地心距离，单位 AU；height 为观测者海拔，单位米。
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// distanceAU is geocentric distance in AU; height is observer elevation in meters.
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func TopocentricEcliptic(date time.Time, lon, lat, observerLon, observerLat, distanceAU, height float64) Ecliptic {
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topLon := basic.TopocentricLo(lon, lat, observerLat, observerLon, jdeUTC(date), distanceAU, height)
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topLat := basic.TopocentricBo(lon, lat, observerLat, observerLon, jdeUTC(date), distanceAU, height)
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return Ecliptic{Lon: topLon, Lat: topLat}
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}
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// AngularSeparation 角距离 / angular separation.
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//
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// 输入为两组赤道坐标，单位度；返回角距离，单位度。
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// Inputs are two equatorial coordinates in degrees; return value is in degrees.
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func AngularSeparation(ra1, dec1, ra2, dec2 float64) float64 {
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return basic.StarAngularSeparation(ra1, dec1, ra2, dec2)
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}
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