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
140 lines
5.0 KiB
Go
140 lines
5.0 KiB
Go
package basic
|
||
|
||
import (
|
||
"math"
|
||
|
||
"b612.me/astro/planet"
|
||
. "b612.me/astro/tools"
|
||
)
|
||
|
||
// SaturnRingParameters 土星环参数 / Saturn ring parameters.
|
||
func SaturnRingParameters(jd float64) (earthLatitude, sunLatitude, positionAngle, deltaU, majorAxis, minorAxis float64) {
|
||
return SaturnRingParametersN(jd, -1)
|
||
}
|
||
|
||
// SaturnRingParametersN 土星环参数（截断版） / truncated Saturn ring parameters.
|
||
func SaturnRingParametersN(jd float64, n int) (earthLatitude, sunLatitude, positionAngle, deltaU, majorAxis, minorAxis float64) {
|
||
inclination, node := saturnRingPlane(jd)
|
||
earthLon, earthLat := SaturnApparentLoBoN(jd, n)
|
||
sunLon, sunLat := saturnRingSunLoBo(jd, n, node)
|
||
|
||
earthLatitude = saturnRingLatitude(inclination, node, earthLon, earthLat)
|
||
sunLatitude = saturnRingLatitude(inclination, node, sunLon, sunLat)
|
||
positionAngle = saturnRingPositionAngle(jd, inclination, node, earthLon, earthLat)
|
||
earthU := saturnRingLongitude(inclination, node, earthLon, earthLat)
|
||
sunU := saturnRingLongitude(inclination, node, sunLon, sunLat)
|
||
deltaU = saturnRingLongitudeDelta(earthU, sunU)
|
||
|
||
earthDistance := EarthSaturnAwayN(jd, n)
|
||
majorAxis = 375.35 / earthDistance
|
||
minorAxis = majorAxis * math.Abs(Sin(earthLatitude))
|
||
return
|
||
}
|
||
|
||
// SaturnRingB 土星环张角 B / Saturn ring opening angle B.
|
||
func SaturnRingB(jd float64) float64 {
|
||
return SaturnRingBN(jd, -1)
|
||
}
|
||
|
||
// SaturnRingBN 土星环张角 B（截断版） / truncated Saturn ring opening angle B.
|
||
func SaturnRingBN(jd float64, n int) float64 {
|
||
earthLatitude, _, _, _, _, _ := SaturnRingParametersN(jd, n)
|
||
return earthLatitude
|
||
}
|
||
|
||
// SaturnRingSunB 土星环太阳侧张角 B' / Sun-side Saturn ring opening angle B'.
|
||
func SaturnRingSunB(jd float64) float64 {
|
||
return SaturnRingSunBN(jd, -1)
|
||
}
|
||
|
||
// SaturnRingSunBN 土星环太阳侧张角 B'（截断版） / truncated Sun-side Saturn ring opening angle B'.
|
||
func SaturnRingSunBN(jd float64, n int) float64 {
|
||
_, sunLatitude, _, _, _, _ := SaturnRingParametersN(jd, n)
|
||
return sunLatitude
|
||
}
|
||
|
||
// SaturnRingPositionAngle 土星环北半短轴位置角 / position angle of Saturn ring northern semiminor axis.
|
||
func SaturnRingPositionAngle(jd float64) float64 {
|
||
return SaturnRingPositionAngleN(jd, -1)
|
||
}
|
||
|
||
// SaturnRingPositionAngleN 土星环北半短轴位置角（截断版） / truncated position angle of Saturn ring northern semiminor axis.
|
||
func SaturnRingPositionAngleN(jd float64, n int) float64 {
|
||
_, _, positionAngle, _, _, _ := SaturnRingParametersN(jd, n)
|
||
return positionAngle
|
||
}
|
||
|
||
// SaturnRingDeltaU 太阳和地球在环面内的土星心黄经差 / difference of Saturnicentric ring longitudes.
|
||
func SaturnRingDeltaU(jd float64) float64 {
|
||
return SaturnRingDeltaUN(jd, -1)
|
||
}
|
||
|
||
// SaturnRingDeltaUN 太阳和地球在环面内的土星心黄经差（截断版） / truncated Saturnicentric ring longitude difference.
|
||
func SaturnRingDeltaUN(jd float64, n int) float64 {
|
||
_, _, _, deltaU, _, _ := SaturnRingParametersN(jd, n)
|
||
return deltaU
|
||
}
|
||
|
||
// SaturnRingAxis 土星环外缘长短轴，单位角秒 / outer ring axes in arcseconds.
|
||
func SaturnRingAxis(jd float64) (majorAxis, minorAxis float64) {
|
||
return SaturnRingAxisN(jd, -1)
|
||
}
|
||
|
||
// SaturnRingAxisN 土星环外缘长短轴（截断版），单位角秒 / truncated outer ring axes in arcseconds.
|
||
func SaturnRingAxisN(jd float64, n int) (majorAxis, minorAxis float64) {
|
||
_, _, _, _, majorAxis, minorAxis = SaturnRingParametersN(jd, n)
|
||
return
|
||
}
|
||
|
||
func saturnRingPlane(jd float64) (inclination, node float64) {
|
||
t := (jd - 2451545.0) / 36525.0
|
||
inclination = 28.075216 - 0.012998*t + 0.000004*t*t
|
||
node = 169.508470 + 1.394681*t + 0.000412*t*t
|
||
return
|
||
}
|
||
|
||
func saturnRingSunLoBo(jd float64, n int, node float64) (lon, lat float64) {
|
||
lon = planet.WherePlanetN(5, 0, jd, n)
|
||
lat = planet.WherePlanetN(5, 1, jd, n)
|
||
distance := planet.WherePlanetN(5, 2, jd, n)
|
||
lat -= 0.000764 * Cos(lon-node) / distance
|
||
lon -= 0.01759 / distance
|
||
return lon, lat
|
||
}
|
||
|
||
func saturnRingLatitude(inclination, node, lon, lat float64) float64 {
|
||
return ArcSin(Sin(inclination)*Cos(lat)*Sin(lon-node) - Cos(inclination)*Sin(lat))
|
||
}
|
||
|
||
func saturnRingLongitude(inclination, node, lon, lat float64) float64 {
|
||
y := Sin(inclination)*Sin(lat) + Cos(inclination)*Cos(lat)*Sin(lon-node)
|
||
x := Cos(lat) * Cos(lon-node)
|
||
return ArcTan2(y, x)
|
||
}
|
||
|
||
func saturnRingLongitudeDelta(a, b float64) float64 {
|
||
delta := math.Abs(Limit360(a - b))
|
||
if delta > 180 {
|
||
return 360 - delta
|
||
}
|
||
return delta
|
||
}
|
||
|
||
func saturnRingPositionAngle(jd, inclination, node, lon, lat float64) float64 {
|
||
poleLon := node - 90 + Nutation2000Bi(jd)
|
||
poleLat := 90 - inclination
|
||
eps := TrueObliquity(jd)
|
||
poleRa, poleDec := saturnRingEclipticToEquatorial(poleLon, poleLat, eps)
|
||
saturnRa, saturnDec := saturnRingEclipticToEquatorial(lon, lat, eps)
|
||
|
||
y := Cos(poleDec) * Sin(poleRa-saturnRa)
|
||
x := Sin(poleDec)*Cos(saturnDec) - Cos(poleDec)*Sin(saturnDec)*Cos(poleRa-saturnRa)
|
||
return ArcTan2(y, x)
|
||
}
|
||
|
||
func saturnRingEclipticToEquatorial(lon, lat, eps float64) (ra, dec float64) {
|
||
ra = ArcTan2(Sin(lon)*Cos(eps)-Tan(lat)*Sin(eps), Cos(lon))
|
||
dec = ArcSin(Sin(lat)*Cos(eps) + Cos(lat)*Sin(eps)*Sin(lon))
|
||
return
|
||
}
|