85 lines
2.9 KiB
Go
85 lines
2.9 KiB
Go
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package basic
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import (
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"math"
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"b612.me/astro/planet"
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. "b612.me/astro/tools"
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)
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type planetGeocentricPosition struct {
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x float64
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y float64
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z float64
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lo float64
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bo float64
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}
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func planetHeliocentricXYZN(planetIndex int, jd float64, n int) (float64, float64, float64) {
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l := planet.WherePlanetN(planetIndex, 0, jd, n)
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b := planet.WherePlanetN(planetIndex, 1, jd, n)
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r := planet.WherePlanetN(planetIndex, 2, jd, n)
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return sphericalToRectangular(l, b, r)
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}
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func earthHeliocentricXYZN(jd float64, n int) (float64, float64, float64) {
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l := planet.WherePlanetN(-1, 0, jd, n)
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b := planet.WherePlanetN(-1, 1, jd, n)
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r := planet.WherePlanetN(-1, 2, jd, n)
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return sphericalToRectangular(l, b, r)
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}
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func sphericalToRectangular(lo, bo, radius float64) (float64, float64, float64) {
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cosBo := math.Cos(bo * math.Pi / 180)
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return radius * cosBo * math.Cos(lo*math.Pi/180),
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radius * cosBo * math.Sin(lo*math.Pi/180),
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radius * math.Sin(bo*math.Pi/180)
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}
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func geocentricPositionFromRectangular(x, y, z float64) planetGeocentricPosition {
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lo := math.Atan2(y, x) * 180 / math.Pi
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bo := math.Atan2(z, math.Sqrt(x*x+y*y)) * 180 / math.Pi
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return planetGeocentricPosition{
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x: x,
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y: y,
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z: z,
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lo: Limit360(lo),
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bo: bo,
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}
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}
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func planetGeocentricPositionN(planetIndex int, planetJD, earthJD float64, n int) planetGeocentricPosition {
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px, py, pz := planetHeliocentricXYZN(planetIndex, planetJD, n)
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ex, ey, ez := earthHeliocentricXYZN(earthJD, n)
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return geocentricPositionFromRectangular(px-ex, py-ey, pz-ez)
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}
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func planetGeocentricPositionWithEarthN(planetIndex int, planetJD float64, ex, ey, ez float64, n int) planetGeocentricPosition {
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px, py, pz := planetHeliocentricXYZN(planetIndex, planetJD, n)
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return geocentricPositionFromRectangular(px-ex, py-ey, pz-ez)
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}
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func planetApparentGeocentricPositionN(planetIndex int, jd float64, n int) (planetGeocentricPosition, float64) {
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ex, ey, ez := earthHeliocentricXYZN(jd, n)
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geoNow := planetGeocentricPositionWithEarthN(planetIndex, jd, ex, ey, ez, n)
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tau := 0.0057755183 * math.Sqrt(geoNow.x*geoNow.x+geoNow.y*geoNow.y+geoNow.z*geoNow.z)
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geo := planetGeocentricPositionWithEarthN(planetIndex, jd-tau, ex, ey, ez, n)
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baseLo := geo.lo
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baseBo := geo.bo
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geo.lo = Limit360(baseLo + GXCLo(baseLo, baseBo, jd)/3600.0 + Nutation2000Bi(jd))
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geo.bo = baseBo + GXCBo(baseLo, baseBo, jd)/3600.0
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return geo, tau
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}
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func planetTrueGeocentricPositionN(planetIndex int, jd float64, n int) (planetGeocentricPosition, float64) {
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ex, ey, ez := earthHeliocentricXYZN(jd, n)
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geoNow := planetGeocentricPositionWithEarthN(planetIndex, jd, ex, ey, ez, n)
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tau := 0.0057755183 * math.Sqrt(geoNow.x*geoNow.x+geoNow.y*geoNow.y+geoNow.z*geoNow.z)
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return planetGeocentricPositionWithEarthN(planetIndex, jd-tau, ex, ey, ez, n), tau
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}
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func planetEarthAwayExplicitN(planetIndex int, jd float64, n int) float64 {
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geoNow := planetGeocentricPositionN(planetIndex, jd, jd, n)
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return math.Sqrt(geoNow.x*geoNow.x + geoNow.y*geoNow.y + geoNow.z*geoNow.z)
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}
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