/// <summary>
/// Calculates phases of the sun for a single day and latitude/longitude
/// and optionally the observer height (in meters) relative to the horizon
/// </summary>
/// <param name="date"></param>
/// <param name="lat"></param>
/// <param name="lng"></param>
/// <param name="height"></param>
/// <returns></returns>
public static IEnumerable <SunPhase> GetSunPhases(DateTimeOffset date, double lat, double lng, double height = 0)
{
var lw = Constants.Rad * -lng;
var phi = Constants.Rad * lat;
var dh = SunTime.GetObserverAngle(height);
var d = date.ToDays();
var n = SunTime.GetJulianCycle(d, lw);
var ds = SunTime.GetApproxTransit(0, lw, n);
var m = Sun.GetMeanAnomaly(ds);
var l = Sun.GetEclipticLongitude(m);
var dec = Position.GetDeclination(l, 0);
var jnoon = SunTime.GetSolarTransitJ(ds, m, l);
var solarNoon = jnoon.FromJulian();
var nadir = (jnoon - 0.5).FromJulian();
var sunPhaseCol = new List <SunPhase>
{
new SunPhase(SunPhaseName.SolarNoon, solarNoon),
new SunPhase(SunPhaseName.Nadir, nadir)
};
foreach (var sunPhase in SunPhaseAngle.List)
{
var h0 = (sunPhase.Angle + dh) * Constants.Rad;
var jset = SunTime.GetSetJ(h0, lw, phi, dec, n, m, l);
if (double.IsNaN(jset) || double.IsInfinity(jset))
{
continue;
}
var jrise = jnoon - (jset - jnoon);
sunPhaseCol.Add(new SunPhase(sunPhase.RiseName, jrise.FromJulian()));
sunPhaseCol.Add(new SunPhase(sunPhase.SetName, jset.FromJulian()));
}
return(sunPhaseCol);
}
