106 lines
5.5 KiB
Go
106 lines
5.5 KiB
Go
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package eclipse
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import "b612.me/astro/basic"
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// SolarEclipseBesselianPolynomial 是三次多项式系数，索引 n 对应 t 的 n 次幂，t 为自 T0 起算的 TT 小时数。
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// SolarEclipseBesselianPolynomial holds the cubic coefficients; index n multiplies t^n with t in TT hours from T0.
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type SolarEclipseBesselianPolynomial = basic.SolarEclipseBesselianPolynomial
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// SolarEclipseBesselianElementsOptions 是贝塞尔根数表的生成选项 / options for a Besselian element table.
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type SolarEclipseBesselianElementsOptions struct {
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// Model 月亮半径模型，零值为 NASA bulletin Split-K / lunar radius model.
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Model SolarEclipseRadiusModel
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// SunRadiusModel 太阳半径口径，零值为标准档 / solar radius convention.
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SunRadiusModel SolarEclipseSunRadiusModel
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// DeltaTSeconds 显式 ΔT（秒），<=0 用进程级模型，只改变地球自转相位 / explicit ΔT in seconds.
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DeltaTSeconds float64
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// ReferenceJDE 多项式参考时刻 T0（TT 儒略日），<=0 取离食甚最近的整 TT 小时 / TT reference instant, the whole hour nearest greatest eclipse.
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ReferenceJDE float64
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// ValidHours 有效窗口半径（小时），<=0 取 3 / validity window half-width in hours.
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ValidHours float64
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}
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// SolarEclipseBesselianElementsResult 是一次日食的多项式贝塞尔根数及其口径 / polynomial Besselian elements and their conventions.
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type SolarEclipseBesselianElementsResult struct {
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// T0JDE 多项式参考时刻（TT 儒略日），t = (jde - T0JDE) * 24 / TT reference instant.
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T0JDE float64
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// ValidHours 有效窗口半径（小时） / validity window half-width.
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ValidHours float64
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// X 与 Y 是月心在基本面内的坐标，单位地球赤道半径 / fundamental-plane coordinates in equatorial Earth radii.
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X, Y SolarEclipseBesselianPolynomial
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// D 是影轴赤纬，单位度 / declination of the shadow axis in degrees.
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D SolarEclipseBesselianPolynomial
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// L1 与 L2 是基本面内的半影、本影半径，单位地球赤道半径；本影为负表示月心尚未越过本影锥顶点。
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// L1 and L2 are the penumbral and umbral radii in the fundamental plane, in equatorial Earth radii.
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L1, L2 SolarEclipseBesselianPolynomial
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// Mu 是影轴格林时角，单位度，窗口内连续、不折回 [0,360)。
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//
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// 口径与已发布根数表不同：本库的恒星时取自 UT = TT - ΔT，得到真实格林时角；已发布表改用 T0 本身
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// 的恒星时，两者相差 ΔT × 15.041067/3600 度。要对表先用 SolarEclipseBesselianMuForPublishedTable。
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// Mu is the shadow axis' Greenwich hour angle in degrees, continuous and not folded into [0,360).
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Mu SolarEclipseBesselianPolynomial
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// TanF1 与 TanF2 是半影、本影锥半顶角正切，本次日食内为常数 / cone half-angle tangents, constant over the eclipse.
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TanF1, TanF2 float64
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// Gamma 是食甚时刻影轴到地心的距离，单位地球赤道半径 / shadow-axis distance from the Earth's centre.
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Gamma float64
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// Magnitude 是食甚时刻的全局食分 / global eclipse magnitude at greatest eclipse.
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Magnitude float64
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// Model、SunRadiusModel、PenumbralK、UmbralK 与 DeltaTSeconds 是决定上述数值的口径 / the conventions behind the numbers above.
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Model SolarEclipseRadiusModel
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SunRadiusModel SolarEclipseSunRadiusModel
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PenumbralK float64
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UmbralK float64
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DeltaTSeconds float64
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}
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// SolarEclipseBesselianElements 计算给定近朔时刻附近一次日食的多项式贝塞尔根数，窗口内无日食时返回 false。
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// Polynomial Besselian elements for the solar eclipse near the given new-moon instant.
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func SolarEclipseBesselianElements(
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seedJDE float64, options SolarEclipseBesselianElementsOptions,
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) (SolarEclipseBesselianElementsResult, bool) {
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result, ok := basic.SolarEclipseBesselianElements(seedJDE, basic.SolarEclipseBesselianElementsOptions{
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Model: basic.SolarEclipseRadiusModel(options.Model),
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SunRadiusModel: basic.SolarEclipseSunRadiusModel(options.SunRadiusModel),
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DeltaTSeconds: options.DeltaTSeconds,
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ReferenceJDE: options.ReferenceJDE,
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ValidHours: options.ValidHours,
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})
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if !ok {
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return SolarEclipseBesselianElementsResult{}, false
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}
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return solarEclipseBesselianElementsFromBasic(result), true
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}
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// SolarEclipseBesselianMuForPublishedTable 把本库的 Mu 换算成与已发布根数表直接可比的取值。
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// 已发布表用 T0 本身的恒星时，本库用 UT = TT - ΔT，两者只差一个常数，因此只有常数项平移。
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// SolarEclipseBesselianMuForPublishedTable shifts Mu onto the argument used by published element tables.
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func SolarEclipseBesselianMuForPublishedTable(
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mu SolarEclipseBesselianPolynomial, deltaTSeconds float64,
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) SolarEclipseBesselianPolynomial {
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return basic.SolarEclipseBesselianMuForPublishedTable(mu, deltaTSeconds)
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}
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func solarEclipseBesselianElementsFromBasic(
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result basic.SolarEclipseBesselianElementsResult,
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) SolarEclipseBesselianElementsResult {
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return SolarEclipseBesselianElementsResult{
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T0JDE: result.T0JDE,
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ValidHours: result.ValidHours,
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X: result.X,
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Y: result.Y,
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D: result.D,
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L1: result.L1,
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L2: result.L2,
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Mu: result.Mu,
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TanF1: result.TanF1,
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TanF2: result.TanF2,
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Gamma: result.Gamma,
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Magnitude: result.Magnitude,
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Model: mapBasicSolarEclipseModel(result.Model),
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SunRadiusModel: result.SunRadiusModel,
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PenumbralK: result.PenumbralK,
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UmbralK: result.UmbralK,
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DeltaTSeconds: result.DeltaTSeconds,
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}
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}
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