/// <summary>
/// Calculate the current phase of the moon.
/// Note: this calculation uses the last recorded new moon to calculate the cycles of
/// of the moon since then. Any date in the past before 1920 might not work.
/// </summary>
/// <param name="utcDateTime"></param>
/// <remarks>https://www.subsystems.us/uploads/9/8/9/4/98948044/moonphase.pdf</remarks>
/// <returns></returns>
public static PhaseResult Calculate(DateTime utcDateTime,
Earth.Hemispheres viewFromEarth = Earth.Hemispheres.Northern)
{
const double julianConstant = 2415018.5;
var julianDate = utcDateTime.ToOADate() + julianConstant;
// London New Moon (1920)
// https://www.timeanddate.com/moon/phases/uk/london?year=1920
var daysSinceLastNewMoon =
new DateTime(1920, 1, 21, 5, 25, 00, DateTimeKind.Utc).ToOADate() + julianConstant;
var newMoons = (julianDate - daysSinceLastNewMoon) / TotalLengthOfCycle;
var intoCycle = (newMoons - Math.Truncate(newMoons)) * TotalLengthOfCycle;
var phase =
allPhases.First(p => intoCycle >= p.Start && intoCycle <= p.End);
var index = allPhases.IndexOf(phase);
var currentPhase =
viewFromEarth switch
{
Earth.Hemispheres.Northern => NorthernHemisphere[index],
_ => SouthernHemisphere[index]
};
return(new PhaseResult
(
phase.Name,
currentPhase,
Math.Round(intoCycle, 2),
viewFromEarth,
utcDateTime
));
}
public PhaseResult(string name, string emoji, double daysIntoCycle, Earth.Hemispheres hemisphere,
DateTime moment)
{
Name = name;
Emoji = emoji;
DaysIntoCycle = daysIntoCycle;
Hemisphere = hemisphere;
Moment = moment;
}
public static PhaseResult Now(Earth.Hemispheres viewFromEarth = Earth.Hemispheres.Northern)
{
return(Calculate(DateTime.Now.ToUniversalTime(), viewFromEarth));
}
public static PhaseResult UtcNow(Earth.Hemispheres viewFromEarth = Earth.Hemispheres.Northern)
{
return(Calculate(DateTime.UtcNow, viewFromEarth));
}
public static PhaseResult PhaseFromUserTime(DateTime userTime, Earth.Hemispheres viewFromEarth = Earth.Hemispheres.Northern) // My addition
{
return(Calculate(userTime, viewFromEarth));
}
