EquatorialCoordinates

public struct EquatorialCoordinates : CustomStringConvertible

The coordinates of an object in the equatorial system, based on Earth equator.

  • The right ascension

    Declaration

    Swift

    public let rightAscension: Hour
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  • The declination

    Declaration

    Swift

    public let declination: Degree
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  • The epoch of the coordinates.

    Declaration

    Swift

    public let epoch: Epoch
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  • The reference equinox.

    Declaration

    Swift

    public let equinox: Equinox
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  • Convenience accessor for the right ascension

    Declaration

    Swift

    public var alpha: Hour { get }
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  • Convenience accessor of the declination

    Declaration

    Swift

    public var delta: Degree { get }
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  • Creates an EquatorialCoordinates instance.

    Declaration

    Swift

    public init(rightAscension: Hour, declination: Degree, epoch: Epoch = .J2000, equinox: Equinox = .standardJ2000)

    Parameters

    rightAscension

    The right ascension value
    declination

    The declination value
    epoch

    The optional epoch, default to J2000.0.
    equinox

    The optional equinox, default to standard equinox J2000.0.
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  • Creates an EquatorialCoordinates instance.

    Declaration

    Swift

    public init(alpha: Hour, delta: Degree, epoch: Epoch = .J2000, equinox: Equinox = .standardJ2000)

    Parameters

    alpha

    The alpha (R.A.) value
    delta

    The delta (Dec.) value
    epoch

    The optional epoch value, default to J2000.0. It is not called ‘epsilon’ to avoid confusion with equinox.
    equinox

    The optional equinox, default to standard equinox J2000.0.
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  • Transform the coordinates to the ecliptic (celestial) system, at same epoch and for the same equinox.

    During the transformation, the mean obliquity of the ecliptic of the date (epoch) is used. Recall that the obliquity of the ecliptic is the inclination of Earth’s rotation axis, or the angle between equator and the ecliptic, that is, the Earth orbital plane. ‘Mean’ here means that nutation is not taken into account.

    Declaration

    Swift

    public func makeEclipticCoordinates() -> EclipticCoordinates

    Return Value

    A new EclipticCoordinates object.

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  • The galactic (Milky Way) North Pole equatorial coordinates.

    These coordinates have been fixed conventionally and must be considered as expect for the equinox B1950. They have been defined by the International Astronomical Union in 1959. The origin of the galactic longitude is the point (in western Sagittarius) of the galactic equator which is 33º distant from the ascending node (in western Aquila) of the galactic equator with the equator of B1950.0. See AA p.94.

    Declaration

    Swift

    public static func adoptedGalacticNorthPole() -> EquatorialCoordinates

    Return Value

    A new EquatorialCoordinates instance.

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  • Transform the coordinates to the galactic system, at same epoch and for the same equinox.

    Declaration

    Swift

    public func makeGalacticCoordinates() -> GalacticCoordinates

    Return Value

    A new galactic coordinates instance.

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  • Transforms the coordinates into horizontal (local) ones for a given observer location.

    Declaration

    Swift

    public func makeHorizontalCoordinates(for location: GeographicCoordinates, at julianDay: JulianDay) -> HorizontalCoordinates

    Parameters

    location

    The geographic location of the observer.
    julianDay

    The julian day of observation.

    Return Value

    A new horizontal coordinates instance.

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  • Returns new EquatorialCoordinates precessed to the given epoch.

    Declaration

    Swift

    public func precessedCoordinates(to newEquinox: Equinox) -> EquatorialCoordinates

    Parameters

    newEquinox

    The new equinox to precess to.

    Return Value

    A new EquatorialCoordinates instance.

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  • Returns new EquatorialCoordinates shifted to the new epoch by the given proper motion.

    Declaration

    Swift

    public func shiftedCoordinates(to newEpoch: Epoch, with properMotion: ProperMotion) -> EquatorialCoordinates

    Parameters

    newEpoch

    The new epoch of coordinates.
    properMotion

    The amount of proper motion

    Return Value

    A new EquatorialCoordinates instance.

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  • Returns the angular separation between two equatorial coordinates.

    Declaration

    Swift

    public func angularSeparation(with otherCoordinates: EquatorialCoordinates) -> Degree

    Parameters

    otherCoordinates

    The other coordinates to consider.

    Return Value

    A angle value, between the two coordinates.

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  • Returns the position angle relative to other coordinates.

    Declaration

    Swift

    public func positionAngle(relativeTo otherCoordinates: EquatorialCoordinates) -> Degree

    Parameters

    otherCoordinates

    The other coordinates.

    Return Value

    The position angle between the two coordinates.

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  • Return new ecliptic coordinates corrected for the annual aberration of the Earth. It must be used for star coordinates, not planets. See AA, p149.

    Declaration

    Swift

    public func correctedForAnnualAberration(julianDay: JulianDay, highPrecision: Bool = true) -> EquatorialCoordinates

    Parameters

    julianDay

    The julian day for which the aberration is computed.
    highPrecision

    If false, the Ron-Vondrák algorithm is used. See AA p.153. If true, the newer VSOP87 theory is used.

    Return Value

    Corected ecliptic coordinates of the star.

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  • Description of EquatorialCoordinates

    Declaration

    Swift

    public var description: String { get }
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