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452 lines
19 KiB
Go
452 lines
19 KiB
Go
package eclipse
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import (
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"math"
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"time"
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"b612.me/astro/basic"
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)
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const (
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solarEclipseSynodicMonthDays = 29.530588853
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solarEclipseSearchLimit = 36
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solarEclipseSearchEpsilonDay = 1e-8
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solarEclipseLatitudeLimitDeg = 2.0
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)
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type solarEclipseCalculator func(float64) basic.SolarEclipseResult
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// SolarEclipseRadiusModel 日食月亮半径模型, lunar radius model for solar eclipses.
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type SolarEclipseRadiusModel string
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const (
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// SolarEclipseModelIAUSingleK IAU 单一 k 值模型, IAU single-k model.
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SolarEclipseModelIAUSingleK SolarEclipseRadiusModel = "iau_single_k"
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// SolarEclipseModelNASABulletinSplitK NASA bulletin 分裂 k 值模型, NASA bulletin split-k model.
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SolarEclipseModelNASABulletinSplitK SolarEclipseRadiusModel = "nasa_bulletin_split_k"
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)
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// SolarEclipseSunRadiusModel 日食太阳半径口径, solar radius convention for solar eclipses.
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type SolarEclipseSunRadiusModel = basic.SolarEclipseSunRadiusModel
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const (
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// SolarEclipseSunRadiusStandard 标准档，1 AU 处 959.639″, standard solar radius for catalogue reproduction.
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SolarEclipseSunRadiusStandard = basic.SolarEclipseSunRadiusStandard
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// SolarEclipseSunRadiusMeasured 边缘档，1 AU 处 959.95″, measured eclipse solar radius.
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SolarEclipseSunRadiusMeasured = basic.SolarEclipseSunRadiusMeasured
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)
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// SolarEclipseOptions 日食搜索的半径口径, radius conventions for a solar eclipse search.
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type SolarEclipseOptions struct {
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// RadiusModel 月亮半径模型，非 IAU Single-K 一律按 NASA bulletin Split-K, lunar radius model.
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RadiusModel 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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}
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// SolarEclipseType 全局日食食型, global solar eclipse type.
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type SolarEclipseType string
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const (
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// SolarEclipseNone 无日食, no solar eclipse.
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SolarEclipseNone SolarEclipseType = "none"
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// SolarEclipsePartial 日偏食, partial solar eclipse.
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SolarEclipsePartial SolarEclipseType = "partial"
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// SolarEclipseAnnular 日环食, annular solar eclipse.
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SolarEclipseAnnular SolarEclipseType = "annular"
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// SolarEclipseTotal 日全食, total solar eclipse.
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SolarEclipseTotal SolarEclipseType = "total"
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// SolarEclipseHybrid 全环食, hybrid solar eclipse.
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SolarEclipseHybrid SolarEclipseType = "hybrid"
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)
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// SolarEclipseCentrality 中心线进入地球的方式, global eclipse centrality.
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type SolarEclipseCentrality string
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const (
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// SolarEclipseNonCentral 非中心食, non-central eclipse.
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SolarEclipseNonCentral SolarEclipseCentrality = "non_central"
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// SolarEclipseCentralOneLimit 单界中心食, central eclipse with one limit.
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SolarEclipseCentralOneLimit SolarEclipseCentrality = "central_one_limit"
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// SolarEclipseCentralTwoLimits 双界中心食, central eclipse with two limits.
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SolarEclipseCentralTwoLimits SolarEclipseCentrality = "central_two_limits"
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)
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// SolarEclipseInfo 全局日食信息, global solar eclipse information.
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//
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// 所有时刻字段都保持用户输入的时区。
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// 不存在的阶段使用零值 time.Time。
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type SolarEclipseInfo struct {
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// Model 日食月亮半径模型, eclipse lunar radius model.
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Model SolarEclipseRadiusModel
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// SunRadiusModel 日食太阳半径口径, solar radius convention.
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SunRadiusModel SolarEclipseSunRadiusModel
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// Type 全局食型, global eclipse type.
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Type SolarEclipseType
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// Centrality 中心性, eclipse centrality.
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Centrality SolarEclipseCentrality
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// HasSaros 存在沙罗序列信息（可能是锚点外推结果）, has Saros series metadata (possibly extrapolated).
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HasSaros bool
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// Saros 是沙罗序列信息，包括系列号、系列内序号和总成员数。
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// Saros is Saros series metadata with the series number, member index, and total member count.
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Saros SarosInfo
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// GreatestEclipse 食甚时刻, greatest eclipse.
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GreatestEclipse time.Time
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// PartialBeginOnEarth 地球范围偏食始, partial eclipse begins on Earth.
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PartialBeginOnEarth time.Time
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// PartialEndOnEarth 地球范围偏食终, partial eclipse ends on Earth.
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PartialEndOnEarth time.Time
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// CentralBeginOnEarth 地球范围中心食始, central eclipse begins on Earth.
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CentralBeginOnEarth time.Time
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// CentralEndOnEarth 地球范围中心食终, central eclipse ends on Earth.
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CentralEndOnEarth time.Time
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// GreatestJDE 是食甚的力学时儒略日；与 DeltaTSeconds 配对即可复现上列民用时刻。
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// GreatestJDE is the TT Julian ephemeris day of greatest eclipse; with DeltaTSeconds it reproduces the civil times above.
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GreatestJDE float64
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// DeltaTSeconds 是本次计算实际使用的 TT−UT1，单位秒。
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// DeltaTSeconds is the TT−UT1 used by this computation, in seconds.
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DeltaTSeconds float64
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// Magnitude 全局食分, global eclipse magnitude.
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Magnitude float64
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// Gamma 食甚时影轴到地心的距离, gamma at greatest eclipse.
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Gamma float64
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// CentralDuration 是食甚点的中心食持续时间，即日食目录（如 NASA「Central Dur.」）
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// 的取值口径；沿整条中心线的最大值见 SolarEclipsePath.MaxCentralDuration。
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// CentralDuration is the central-phase duration at the greatest eclipse, the
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// value catalogues publish; SolarEclipsePath.MaxCentralDuration is the maximum
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// along the whole track.
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CentralDuration time.Duration
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// PathWidthKM 是食甚处中心食带宽度；非中心食为 0；单侧极限（中心带仅触及地球边缘）时该解析式失效
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// 并一并置 0，此时 PathWidthDefined 为 false，NASA 目录该栏印 '-'。
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// PathWidthKM is the central path width at greatest eclipse, 0 for a non-central
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// event, and 0 when the analytic formula fails at a single-sided limit where the
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// band only grazes the Earth's limb; PathWidthDefined is false there and
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// catalogues print '-' for this column.
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PathWidthKM float64
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// PathWidthDefined 表示上面的带宽是否有定义：只有南北两限都存在时才为 true。
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// PathWidthDefined reports whether the width above is defined: it is true only
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// when both band limits exist.
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PathWidthDefined bool
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// GreatestLongitude 食甚点经度，东正西负, longitude of greatest eclipse, east positive.
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GreatestLongitude float64
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// GreatestLatitude 食甚点纬度，北正南负, latitude of greatest eclipse, north positive.
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GreatestLatitude float64
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// HasPartial 存在偏食阶段, has partial phase.
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HasPartial bool
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// HasCentral 存在中心食阶段, has central phase.
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HasCentral bool
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// HasAnnular 存在环食阶段, has annular phase.
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HasAnnular bool
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// HasTotal 存在全食阶段, has total phase.
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HasTotal bool
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// HasHybrid 为混合食, is hybrid eclipse.
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HasHybrid bool
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}
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// SolarEclipseOnDate 当地自然日全局日食查询 / local-date global solar eclipse query.
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// Determine whether a global solar eclipse overlaps the local date, using NASA bulletin Split-K by default.
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func SolarEclipseOnDate(date time.Time) (SolarEclipseInfo, bool) {
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return SolarEclipseOnDateNASABulletinSplitK(date)
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}
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// SolarEclipseOnDateNASABulletinSplitK 当地自然日全局日食查询（NASA bulletin Split-K） / local-date global solar eclipse query with NASA bulletin Split-K.
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// Determine whether a global solar eclipse overlaps the local date with the NASA bulletin Split-K model.
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func SolarEclipseOnDateNASABulletinSplitK(date time.Time) (SolarEclipseInfo, bool) {
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return solarEclipseOnDate(date, basic.SolarEclipseNASABulletinSplitK)
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}
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// SolarEclipseOnDateIAUSingleK 当地自然日全局日食查询（IAU Single-K） / local-date global solar eclipse query with IAU Single-K.
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// Determine whether a global solar eclipse overlaps the local date with the IAU Single-K model.
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func SolarEclipseOnDateIAUSingleK(date time.Time) (SolarEclipseInfo, bool) {
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return solarEclipseOnDate(date, basic.SolarEclipseIAUSingleK)
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}
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// SolarEclipseOnDateWithOptions 当地自然日全局日食查询（自定义半径口径） / local-date global solar eclipse query with custom radius conventions.
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func SolarEclipseOnDateWithOptions(date time.Time, options SolarEclipseOptions) (SolarEclipseInfo, bool) {
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return solarEclipseOnDate(date, solarEclipseCalculatorFor(options))
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}
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// LastSolarEclipseWithOptions 上次日食（自定义半径口径） / previous solar eclipse with custom radius conventions.
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func LastSolarEclipseWithOptions(date time.Time, options SolarEclipseOptions) SolarEclipseInfo {
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info, _ := searchSolarEclipse(date, -1, true, solarEclipseCalculatorFor(options))
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return info
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}
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// NextSolarEclipseWithOptions 下次日食（自定义半径口径） / next solar eclipse with custom radius conventions.
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func NextSolarEclipseWithOptions(date time.Time, options SolarEclipseOptions) SolarEclipseInfo {
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info, _ := searchSolarEclipse(date, 1, false, solarEclipseCalculatorFor(options))
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return info
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}
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// ClosestSolarEclipseWithOptions 最近一次日食（自定义半径口径） / closest solar eclipse with custom radius conventions.
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func ClosestSolarEclipseWithOptions(date time.Time, options SolarEclipseOptions) SolarEclipseInfo {
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last, hasLast := searchSolarEclipse(date, -1, true, solarEclipseCalculatorFor(options))
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next, hasNext := searchSolarEclipse(date, 1, false, solarEclipseCalculatorFor(options))
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return closestSolarEclipse(date, last, hasLast, next, hasNext)
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}
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func solarEclipseCalculatorFor(options SolarEclipseOptions) solarEclipseCalculator {
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basicOptions := basic.SolarEclipseOptions{
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RadiusModel: basic.SolarEclipseRadiusModel(options.RadiusModel),
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SunRadiusModel: basic.SolarEclipseSunRadiusModel(options.SunRadiusModel),
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}
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if basicOptions.RadiusModel != basic.SolarEclipseModelIAUSingleK {
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basicOptions.RadiusModel = basic.SolarEclipseModelNASABulletinSplitK
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}
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return func(seed float64) basic.SolarEclipseResult {
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return basic.SolarEclipseWithOptions(seed, basicOptions)
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}
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}
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func solarEclipseOnDate(date time.Time, calculator solarEclipseCalculator) (SolarEclipseInfo, bool) {
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location := date.Location()
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dayStart, dayMid, dayEnd := solarEclipseLocalDayBounds(date)
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candidateTT := basic.CalcMoonSHByJDE(solarEclipseTimeToTTJDE(dayMid), 0)
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result := calculator(candidateTT)
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if result.Type == basic.SolarEclipseNone {
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return SolarEclipseInfo{}, false
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}
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info := solarEclipseInfoFromBasic(result, location)
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if !solarEclipseOverlapsDate(info, dayStart, dayEnd) {
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return SolarEclipseInfo{}, false
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}
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return info, true
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}
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// LastSolarEclipse 上次日食 / previous solar eclipse.
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// Previous solar eclipse, using NASA bulletin Split-K by default.
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func LastSolarEclipse(date time.Time) SolarEclipseInfo {
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return LastSolarEclipseNASABulletinSplitK(date)
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}
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// LastSolarEclipseNASABulletinSplitK 上次日食（NASA bulletin Split-K） / previous solar eclipse with NASA bulletin Split-K.
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// Previous solar eclipse with the NASA bulletin Split-K model.
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func LastSolarEclipseNASABulletinSplitK(date time.Time) SolarEclipseInfo {
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info, _ := searchSolarEclipse(date, -1, true, basic.SolarEclipseNASABulletinSplitK)
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return info
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}
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// LastSolarEclipseIAUSingleK 上次日食（IAU Single-K） / previous solar eclipse with IAU Single-K.
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// Previous solar eclipse with the IAU Single-K model.
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func LastSolarEclipseIAUSingleK(date time.Time) SolarEclipseInfo {
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info, _ := searchSolarEclipse(date, -1, true, basic.SolarEclipseIAUSingleK)
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return info
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}
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// NextSolarEclipse 下次日食 / next solar eclipse.
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// Next solar eclipse, using NASA bulletin Split-K by default.
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func NextSolarEclipse(date time.Time) SolarEclipseInfo {
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return NextSolarEclipseNASABulletinSplitK(date)
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}
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// NextSolarEclipseNASABulletinSplitK 下次日食（NASA bulletin Split-K） / next solar eclipse with NASA bulletin Split-K.
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// Next solar eclipse with the NASA bulletin Split-K model.
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func NextSolarEclipseNASABulletinSplitK(date time.Time) SolarEclipseInfo {
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info, _ := searchSolarEclipse(date, 1, false, basic.SolarEclipseNASABulletinSplitK)
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return info
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}
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// NextSolarEclipseIAUSingleK 下次日食（IAU Single-K） / next solar eclipse with IAU Single-K.
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// Next solar eclipse with the IAU Single-K model.
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func NextSolarEclipseIAUSingleK(date time.Time) SolarEclipseInfo {
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info, _ := searchSolarEclipse(date, 1, false, basic.SolarEclipseIAUSingleK)
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return info
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}
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// ClosestSolarEclipse 最近一次日食 / closest solar eclipse.
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// Closest solar eclipse, using NASA bulletin Split-K by default.
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func ClosestSolarEclipse(date time.Time) SolarEclipseInfo {
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return ClosestSolarEclipseNASABulletinSplitK(date)
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}
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// ClosestSolarEclipseNASABulletinSplitK 最近一次日食（NASA bulletin Split-K） / closest solar eclipse with NASA bulletin Split-K.
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// Closest solar eclipse with the NASA bulletin Split-K model.
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func ClosestSolarEclipseNASABulletinSplitK(date time.Time) SolarEclipseInfo {
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last, hasLast := searchSolarEclipse(date, -1, true, basic.SolarEclipseNASABulletinSplitK)
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next, hasNext := searchSolarEclipse(date, 1, false, basic.SolarEclipseNASABulletinSplitK)
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return closestSolarEclipse(date, last, hasLast, next, hasNext)
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}
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// ClosestSolarEclipseIAUSingleK 最近一次日食（IAU Single-K） / closest solar eclipse with IAU Single-K.
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// Closest solar eclipse with the IAU Single-K model.
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func ClosestSolarEclipseIAUSingleK(date time.Time) SolarEclipseInfo {
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last, hasLast := searchSolarEclipse(date, -1, true, basic.SolarEclipseIAUSingleK)
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next, hasNext := searchSolarEclipse(date, 1, false, basic.SolarEclipseIAUSingleK)
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return closestSolarEclipse(date, last, hasLast, next, hasNext)
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}
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func closestSolarEclipse(
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date time.Time,
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last SolarEclipseInfo,
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hasLast bool,
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next SolarEclipseInfo,
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hasNext bool,
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) SolarEclipseInfo {
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switch {
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case hasLast && !hasNext:
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return last
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case !hasLast && hasNext:
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return next
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case !hasLast && !hasNext:
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return SolarEclipseInfo{}
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}
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lastDistance := math.Abs(date.Sub(last.GreatestEclipse).Seconds())
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nextDistance := math.Abs(next.GreatestEclipse.Sub(date).Seconds())
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if lastDistance <= nextDistance {
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return last
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}
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return next
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}
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func searchSolarEclipse(
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date time.Time,
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direction int,
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includeCurrent bool,
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calculator solarEclipseCalculator,
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) (SolarEclipseInfo, bool) {
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targetTT := solarEclipseTimeToTTJDE(date)
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candidateTT := basic.CalcMoonSHByJDE(targetTT, 0)
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for i := 0; i < solarEclipseSearchLimit; i++ {
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if isPotentialSolarEclipse(candidateTT) {
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result := calculator(candidateTT)
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if result.Type != basic.SolarEclipseNone && solarEclipseMatchesDirection(result.GreatestEclipse, targetTT, direction, includeCurrent) {
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return solarEclipseInfoFromBasic(result, date.Location()), true
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}
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}
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candidateTT = nextEclipseSearchCandidateTT(candidateTT, 0, direction, solarEclipseSynodicMonthDays)
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}
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return SolarEclipseInfo{}, false
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}
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func isPotentialSolarEclipse(newMoonTT float64) bool {
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return math.Abs(basic.HMoonTrueBo(newMoonTT)) <= solarEclipseLatitudeLimitDeg
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}
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func solarEclipseMatchesDirection(greatestTT, targetTT float64, direction int, includeCurrent bool) bool {
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delta := greatestTT - targetTT
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if math.Abs(delta) <= solarEclipseSearchEpsilonDay {
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return direction < 0 && includeCurrent
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}
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if direction > 0 {
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return delta > 0
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}
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return delta < 0
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}
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func solarEclipseLocalDayBounds(date time.Time) (time.Time, time.Time, time.Time) {
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location := date.Location()
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dayStart := time.Date(date.Year(), date.Month(), date.Day(), 0, 0, 0, 0, location)
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dayMid := time.Date(date.Year(), date.Month(), date.Day(), 12, 0, 0, 0, location)
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dayEnd := time.Date(date.Year(), date.Month(), date.Day()+1, 0, 0, 0, 0, location)
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return dayStart, dayMid, dayEnd
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}
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func nextSolarEclipseLocalDayStart(dayStart time.Time) time.Time {
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location := dayStart.Location()
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return time.Date(dayStart.Year(), dayStart.Month(), dayStart.Day()+1, 0, 0, 0, 0, location)
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}
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func solarEclipseInfoFromBasic(result basic.SolarEclipseResult, location *time.Location) SolarEclipseInfo {
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saros, hasSaros := solarSarosInfo(result.GreatestEclipse)
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return SolarEclipseInfo{
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Model: mapBasicSolarEclipseModel(result.Model),
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SunRadiusModel: result.SunRadiusModel,
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Type: mapBasicSolarEclipseType(result.Type),
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Centrality: mapBasicSolarEclipseCentrality(result.Centrality),
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HasSaros: hasSaros,
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Saros: saros,
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GreatestEclipse: solarEclipseTTJDEToTime(result.GreatestEclipse, location),
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PartialBeginOnEarth: solarEclipseTTJDEToTime(result.PartialBeginOnEarth, location),
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PartialEndOnEarth: solarEclipseTTJDEToTime(result.PartialEndOnEarth, location),
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CentralBeginOnEarth: solarEclipseTTJDEToTime(result.CentralBeginOnEarth, location),
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CentralEndOnEarth: solarEclipseTTJDEToTime(result.CentralEndOnEarth, location),
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GreatestJDE: result.GreatestEclipse,
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DeltaTSeconds: basic.DeltaT(result.GreatestEclipse, true),
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Magnitude: result.Magnitude,
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Gamma: result.Gamma,
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CentralDuration: solarEclipseDurationFromDays(result.CentralDurationDays),
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PathWidthKM: result.PathWidthKM,
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PathWidthDefined: result.PathWidthDefined,
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GreatestLongitude: result.GreatestLongitude,
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GreatestLatitude: result.GreatestLatitude,
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HasPartial: result.HasPartial,
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HasCentral: result.HasCentral,
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HasAnnular: result.HasAnnular,
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HasTotal: result.HasTotal,
|
||
HasHybrid: result.HasHybrid,
|
||
}
|
||
}
|
||
|
||
func mapBasicSolarEclipseModel(model basic.SolarEclipseRadiusModel) SolarEclipseRadiusModel {
|
||
switch model {
|
||
case basic.SolarEclipseModelIAUSingleK:
|
||
return SolarEclipseModelIAUSingleK
|
||
default:
|
||
return SolarEclipseModelNASABulletinSplitK
|
||
}
|
||
}
|
||
|
||
func mapBasicSolarEclipseType(eclipseType basic.SolarEclipseType) SolarEclipseType {
|
||
switch eclipseType {
|
||
case basic.SolarEclipsePartial:
|
||
return SolarEclipsePartial
|
||
case basic.SolarEclipseAnnular:
|
||
return SolarEclipseAnnular
|
||
case basic.SolarEclipseTotal:
|
||
return SolarEclipseTotal
|
||
case basic.SolarEclipseHybrid:
|
||
return SolarEclipseHybrid
|
||
default:
|
||
return SolarEclipseNone
|
||
}
|
||
}
|
||
|
||
func mapBasicSolarEclipseCentrality(centrality basic.SolarEclipseCentrality) SolarEclipseCentrality {
|
||
switch centrality {
|
||
case basic.SolarEclipseCentralOneLimit:
|
||
return SolarEclipseCentralOneLimit
|
||
case basic.SolarEclipseCentralTwoLimits:
|
||
return SolarEclipseCentralTwoLimits
|
||
default:
|
||
return SolarEclipseNonCentral
|
||
}
|
||
}
|
||
|
||
func solarEclipseOverlapsDate(info SolarEclipseInfo, dayStart, dayEnd time.Time) bool {
|
||
eventStart, eventEnd, ok := solarEclipseRange(info)
|
||
if !ok {
|
||
return false
|
||
}
|
||
return !eventEnd.Before(dayStart) && eventStart.Before(dayEnd)
|
||
}
|
||
|
||
func solarEclipseRange(info SolarEclipseInfo) (time.Time, time.Time, bool) {
|
||
if !info.HasPartial {
|
||
return time.Time{}, time.Time{}, false
|
||
}
|
||
return info.PartialBeginOnEarth, info.PartialEndOnEarth, true
|
||
}
|
||
|
||
func solarEclipseTTJDEToTime(ttJDE float64, location *time.Location) time.Time {
|
||
// 回填的是民用时刻，偏移必须与正向的 UTC2TT 成对（窗口内即闰秒表，窗口外按未来政策）。
|
||
// 用 ΔT（TT−UT1）会让时刻整体偏一个 DUT1，并破坏等时线网格的整刻度对齐。
|
||
if ttJDE == 0 || math.IsNaN(ttJDE) || math.IsInf(ttJDE, 0) {
|
||
return time.Time{}
|
||
}
|
||
return basic.JD2DateByZone(basic.TT2UTC(ttJDE), location, false)
|
||
}
|
||
|
||
func solarEclipseTimeToTTJDE(date time.Time) float64 {
|
||
utcJD := basic.Date2JD(date.UTC())
|
||
return basic.UTC2TT(utcJD)
|
||
}
|