53 lines
1.7 KiB
Go
53 lines
1.7 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/tools"
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)
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const (
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sunPhysicalInclinationDeg = 7.25
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sunPhysicalKBaseDeg = 73.6667
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sunPhysicalKRateDeg = 1.3958333
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sunCarringtonStartJD = 2398220.0
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sunCarringtonRotationDays = 25.38
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sunPhysicalKEpochJD = 2396758.0
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)
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// SunPhysicalInfo 太阳物理观测参数 / physical observing parameters of the Sun.
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type SunPhysicalInfo struct {
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// P 太阳北极位置角，单位度 / position angle of the solar north pole in degrees.
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P float64
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// B0 日面中心太阳纬度，单位度 / heliographic latitude of the disk center in degrees.
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B0 float64
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// L0 日面中心卡林顿经度，单位度 / Carrington heliographic longitude of the disk center in degrees.
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L0 float64
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}
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// SunPhysical 太阳物理观测参数 / physical observing parameters of the Sun.
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func SunPhysical(jd float64) SunPhysicalInfo {
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return SunPhysicalN(jd, -1)
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}
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// SunPhysicalN 太阳物理观测参数（截断版） / truncated physical observing parameters of the Sun.
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func SunPhysicalN(jd float64, n int) SunPhysicalInfo {
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lambda := HSunApparentLoN(jd, n)
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epsilon := TrueObliquity(jd)
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k := sunPhysicalKBaseDeg + sunPhysicalKRateDeg*(jd-sunPhysicalKEpochJD)/36525.0
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theta := (jd - sunCarringtonStartJD) * 360.0 / sunCarringtonRotationDays
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x := math.Atan(-Cos(lambda)*Tan(epsilon)) * 180.0 / math.Pi
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y := math.Atan(-Cos(lambda-k)*Tan(sunPhysicalInclinationDeg)) * 180.0 / math.Pi
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p := Limit360(x + y)
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b0 := ArcSin(Sin(lambda-k) * Sin(sunPhysicalInclinationDeg))
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eta := ArcTan2(-Sin(lambda-k)*Cos(sunPhysicalInclinationDeg), -Cos(lambda-k))
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l0 := Limit360(eta - theta)
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return SunPhysicalInfo{
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P: p,
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B0: b0,
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L0: l0,
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}
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}
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