/// <summary>
/// Calculates the position of the Sun on the Ecliptic for the given Julian Day
/// </summary>
/// <param name="n">The Julian Day</param>
/// <returns>The position of the sun on the ecliptic</returns>
public static GeocentricEclipticSphericalPosition ToGeocentricEclipticSphericalFromJulianDay(this float n)
{
var L_deg = (280.460f + (0.9856474f * n)).Repeat(360f);
var g_deg = (357.528f + (0.9856003f * n)).Repeat(360f);
var g_rad = Degrees.Radians(g_deg);
var sin_g = Sin(g_rad);
var cos_g = Cos(g_rad);
var lambda_deg = ((float)(L_deg + (1.915f * sin_g) + (0.020f * 2 * sin_g * cos_g))).Repeat(360);
var R = 1.00014f - (0.01671f * cos_g) - (0.00014f * ((cos_g * cos_g) - (sin_g * sin_g)));
var ec = new GeocentricEclipticSphericalPosition(0, lambda_deg, (float)R);
return(ec);
}
/// <summary>
/// This calculation is only good for the Sun, as it does not take the Ecliptic Latitude into consideration.
/// </summary>
/// <param name="n">The Julian Day</param>
/// <returns>The position of the son on the equitorial plane</returns>
public static EquitorialSphericalPosition ToEquitorial(this GeocentricEclipticSphericalPosition p, float n)
{
if (p is null)
{
throw new ArgumentNullException(nameof(p));
}
var epsilon_deg = 23.439f - (0.0000004f * n);
var epsilon_rad = Degrees.Radians(epsilon_deg);
var sin_epsilon = Sin(epsilon_rad);
var cos_epsilon = Cos(epsilon_rad);
var lambda_rad = Degrees.Radians(p.LongitudeDegrees);
var sin_lambda = Sin(lambda_rad);
var cos_lambda = Cos(lambda_rad);
var alpha_rad = (float)Atan2(cos_epsilon * sin_lambda, cos_lambda);
var delta_rad = (float)Asin(sin_epsilon * sin_lambda);
return(new EquitorialSphericalPosition(
Radians.Degrees(alpha_rad),
Radians.Degrees(delta_rad),
p.RadiusAU));
}
