/// <summary>
/// Calculates parameter Q descibing the visibility of lunar crescent.
/// Used for calculating noumenia and epimenia events.
/// </summary>
public double CrescentQ(SkyContext c)
{
var eclSun = c.Get(SunEcliptical);
var eclMoon = c.Get(Ecliptical0);
var sd = c.Get(Semidiameter);
return(LunarEphem.CrescentQ(eclMoon, eclSun, sd, c.Epsilon, c.SiderealTime, c.GeoLocation));
}
public void Noumenia()
{
// Example are taken from
// http://www.makkahcalendar.org/en/islamicCalendarArticle4.php
// IX.4 Example of Makkah
{
// 17 Nov 2009, "best time" is 14:48 UTC
double jd = new Date(new DateTime(2009, 11, 17, 14, 48, 0, DateTimeKind.Utc)).ToJulianEphemerisDay();
// Nutation elements
var nutation = Nutation.NutationElements(jd);
// True obliquity
var epsilon = Date.TrueObliquity(jd, nutation.deltaEpsilon);
// Sidereal time at Greenwich
double siderealTime = Date.ApparentSiderealTime(jd, nutation.deltaPsi, epsilon);
// Ecliptical coordinates of the Sun, taken from the example (see ref.)
CrdsEcliptical eclSun = new CrdsEcliptical(235.39, 0);
// Ecliptical coordinates of the Moon, taken from the example (see ref.)
CrdsEcliptical eclMoon = new CrdsEcliptical(245.01, -3.76);
// Geograhical coordinates of Makkah
CrdsGeographical geo = new CrdsGeographical(-39.82563, 21.42664);
double q = LunarEphem.CrescentQ(eclMoon, eclSun, 0.2539 * 3600, epsilon, siderealTime, geo);
Assert.AreEqual(-0.465, q, 0.001);
}
// IX.5 Example of intermediate horizon 30°W, 30°S at 21:04
{
// 17 Nov 2009, 21:04 UTC
double jd = new Date(new DateTime(2009, 11, 17, 21, 04, 0, DateTimeKind.Utc)).ToJulianEphemerisDay();
// Nutation elements
var nutation = Nutation.NutationElements(jd);
// True obliquity
var epsilon = Date.TrueObliquity(jd, nutation.deltaEpsilon);
// Sidereal time at Greenwich
double siderealTime = Date.ApparentSiderealTime(jd, nutation.deltaPsi, epsilon);
// Ecliptical coordinates of the Sun, taken from the example (see ref.)
CrdsEcliptical eclSun = new CrdsEcliptical(235.65, 0);
// Ecliptical coordinates of the Moon, taken from the example (see ref.)
CrdsEcliptical eclMoon = new CrdsEcliptical(248.32, -3.55);
// Geograhical coordinates of Makkah
CrdsGeographical geo = new CrdsGeographical(30, -30);
double q = LunarEphem.CrescentQ(eclMoon, eclSun, 0.2536 * 3600, epsilon, siderealTime, geo);
Assert.AreEqual(0.367, q, 0.001);
}
}