astro/basic/rise_set.go

package basic

import (
	"errors"
	"math"

	. "b612.me/astro/tools"
)

var (
	// ErrNeverRise/ErrNeverSet 是几何口径：天体全天在地平线以下报 ErrNeverRise（无升起），
	// 全天在地平线以上报 ErrNeverSet（无落下）。名字描述“缺失的那个现象”，不是“被问的事件”；
	// 太阳、恒星、月球三条链路都按此约定，GetMoonRiseTime 因此在极昼返回 ErrNeverSet。
	ErrNeverRise               = errors.New("rise event does not occur on this date")
	ErrNeverSet                = errors.New("set event does not occur on this date")
	ErrNotOnThisDate           = errors.New("rise/set event occurs on adjacent date")
	ErrInvalidObservationInput = errors.New("invalid observation input")
)

func StandardAltitudeStar(aero bool, observerHeight, lat float64) float64 {
	targetAltitude := 0.0
	if aero {
		targetAltitude = -0.566667
	}
	return targetAltitude - HeightDegreeByLat(observerHeight, lat)
}

func StandardAltitudeSun(zenithShift, observerHeight, lat float64) float64 {
	targetAltitude := 0.0
	if zenithShift != 0 {
		targetAltitude = -0.8333
	}
	return targetAltitude - HeightDegreeByLat(observerHeight, lat)
}

func StandardAltitudePlanet(aeroCorrection, observerHeight, lat float64) float64 {
	targetAltitude := 0.0
	if aeroCorrection != 0 {
		targetAltitude = -0.566667
	}
	return targetAltitude - HeightDegreeByLat(observerHeight, lat)
}

func StandardAltitudeMoon(zenithShift, observerHeight, lat float64) float64 {
	targetAltitude := 0.0
	if zenithShift != 0 {
		targetAltitude = -0.83333
	}
	return targetAltitude - HeightDegreeByLat(observerHeight, lat)
}

type planetCulminationFunc func(float64, float64, float64) float64
type planetHeightFunc func(float64, float64, float64, float64) float64
type planetDeclinationFunc func(float64) float64

func planetRiseDown(jd, lon, lat, timezone, aeroCorrection, observerHeight float64, isRise bool, culmination planetCulminationFunc, height planetHeightFunc, declination planetDeclinationFunc) (float64, error) {
	if !isFiniteFloat(jd) || !isFiniteFloat(lon) || !isFiniteFloat(lat) || !isFiniteFloat(timezone) || !isFiniteFloat(aeroCorrection) || !isFiniteFloat(observerHeight) {
		return 0, ErrInvalidObservationInput
	}
	jd = math.Floor(jd) + 0.5
	localTimezone := math.Round(lon / 15)
	targetAltitude := StandardAltitudePlanet(aeroCorrection, observerHeight, lat)

	culminationJD := culmination(jd, lon, localTimezone)
	if !isFiniteFloat(culminationJD) {
		return 0, ErrInvalidObservationInput
	}
	culminationHeight := height(culminationJD, lon, lat, localTimezone)
	previousHeight := height(culminationJD-0.5, lon, lat, localTimezone)
	if !isFiniteFloat(culminationHeight) || !isFiniteFloat(previousHeight) {
		return 0, ErrInvalidObservationInput
	}
	if culminationHeight < targetAltitude {
		return 0, ErrNeverRise
	}
	if previousHeight > targetAltitude {
		return 0, ErrNeverSet
	}

	dec := declination(UTC2TT(culminationJD - localTimezone/24))
	cosHourAngle := (Sin(targetAltitude) - Sin(dec)*Sin(lat)) / (Cos(dec) * Cos(lat))
	if !isFiniteFloat(dec) || !isFiniteFloat(cosHourAngle) {
		return 0, ErrInvalidObservationInput
	}

	var eventJD float64
	if math.Abs(cosHourAngle) <= 1 {
		hourOffset := ArcCos(cosHourAngle) / 15
		if isRise {
			eventJD = culminationJD - hourOffset/24 - 25.0/24.0/60.0
		} else {
			eventJD = culminationJD + hourOffset/24 - 25.0/24.0/60.0
		}
	} else {
		eventJD = culminationJD
		steps := 0
		for height(eventJD, lon, lat, localTimezone) > targetAltitude {
			steps++
			if isRise {
				eventJD -= 15.0 / 60.0 / 24.0
			} else {
				eventJD += 15.0 / 60.0 / 24.0
			}
			if steps > 48 {
				break
			}
		}
	}

	estimateJD, ok := eventNewtonRefine(eventJD, 0.00001, func(prevJD float64) float64 {
		altitudeDelta := height(prevJD, lon, lat, localTimezone) - targetAltitude
		altitudeSlope := (height(prevJD+0.000005, lon, lat, localTimezone) - height(prevJD-0.000005, lon, lat, localTimezone)) / 0.00001
		return altitudeDelta / altitudeSlope
	})
	if !ok {
		return 0, ErrInvalidObservationInput
	}
	return estimateJD - localTimezone/24 + timezone/24, nil
}