astro/eclipse/observation_helpers.go

package eclipse

import (
	"time"

	"b612.me/astro/basic"
	"b612.me/astro/tools"
)

func moonSunLoDiff(date time.Time) float64 {
	jde := basic.UTC2TT(basic.Date2JD(date.UTC()))
	sunLo := basic.HSunApparentLo(jde)
	moonLo := basic.HMoonApparentLo(jde)
	return tools.Limit360(moonLo - sunLo)
}

func solarAltitude(date time.Time, lon, lat float64) float64 {
	localJD := basic.Date2JD(date)
	_, loc := date.Zone()
	return basic.SunHeight(localJD, lon, lat, float64(loc)/3600.0)
}

func solarCulminationTime(date time.Time, lon float64) time.Time {
	localJD := basic.Date2JD(date.Add(time.Duration(-1*date.Hour())*time.Hour)) + 0.5
	_, loc := date.Zone()
	timezone := float64(loc) / 3600.0
	calcJD := basic.CulminationTime(localJD, lon, timezone) - timezone/24.0
	return basic.JD2DateByZone(calcJD, date.Location(), false)
}

func lunarAzimuth(date time.Time, lon, lat float64) float64 {
	localJD := basic.Date2JD(date)
	_, loc := date.Zone()
	return basic.HMoonAzimuth(localJD, lon, lat, float64(loc)/3600.0)
}

func lunarAltitude(date time.Time, lon, lat float64) float64 {
	localJD := basic.Date2JD(date)
	_, loc := date.Zone()
	return basic.HMoonHeight(localJD, lon, lat, float64(loc)/3600.0)
}