Class CalendarAstronomer

java.lang.Object
org.graalvm.shadowed.com.ibm.icu.impl.CalendarAstronomer
public class CalendarAstronomer extends Object
CalendarAstronomer is a class that can perform the calculations to determine the positions of the sun and moon, the time of sunrise and sunset, and other astronomy-related data. The calculations it performs are in some cases quite complicated, and this utility class saves you the trouble of worrying about them.

The measurement of time is a very important part of astronomy. Because astronomical bodies are constantly in motion, observations are only valid at a given moment in time. Accordingly, each CalendarAstronomer object has a time property that determines the date and time for which its calculations are performed. You can set and retrieve this property with setDate, getDate and related methods.

Almost all of the calculations performed by this class, or by any astronomer, are approximations to various degrees of accuracy. The calculations in this class are mostly modelled after those described in the book Practical Astronomy With Your Calculator, by Peter J. Duffett-Smith, Cambridge University Press, 1990. This is an excellent book, and if you want a greater understanding of how these calculations are performed it a very good, readable starting point.

WARNING: This class is very early in its development, and it is highly likely that its API will change to some degree in the future. At the moment, it basically does just enough to support IslamicCalendar and ChineseCalendar.

  • Nested Class Summary

    Nested Classes
    Modifier and Type
    Class
    Description
    static final class 
    CalendarAstronomer.Ecliptic
    Represents the position of an object in the sky relative to the ecliptic, the plane of the earth's orbit around the Sun.
    static final class 
    CalendarAstronomer.Equatorial
    Represents the position of an object in the sky relative to the plane of the earth's equator.
    static final class 
    CalendarAstronomer.Horizon
    Represents the position of an object in the sky relative to the local horizon.

  • Field Summary

    Fields
    Modifier and Type
    Field
    Description
    static final org.graalvm.shadowed.com.ibm.icu.impl.CalendarAstronomer.SolarLongitude
    AUTUMN_EQUINOX
    Constant representing the autumnal equinox.
    static final long
    DAY_MS
    The number of milliseconds in one day.
    static final org.graalvm.shadowed.com.ibm.icu.impl.CalendarAstronomer.MoonAge
    FIRST_QUARTER
    Constant representing the moon's first quarter.
    static final org.graalvm.shadowed.com.ibm.icu.impl.CalendarAstronomer.MoonAge
    FULL_MOON
    Constant representing a full moon.
    static final int
    HOUR_MS
    The number of milliseconds in one hour.
    static final long
    JULIAN_EPOCH_MS
    The start of the julian day numbering scheme used by astronomers, which is 1/1/4713 BC (Julian), 12:00 GMT.
    static final org.graalvm.shadowed.com.ibm.icu.impl.CalendarAstronomer.MoonAge
    LAST_QUARTER
    Constant representing the moon's last quarter.
    static final int
    MINUTE_MS
    The number of milliseconds in one minute.
    static final org.graalvm.shadowed.com.ibm.icu.impl.CalendarAstronomer.MoonAge
    NEW_MOON
    Constant representing a new moon.
    static final int
    SECOND_MS
    The number of milliseconds in one second.
    static final double
    SIDEREAL_DAY
    The number of standard hours in one sidereal day.
    static final double
    SIDEREAL_MONTH
    The average number of days it takes for the moon to return to the same ecliptic longitude relative to the stellar background.
    static final double
    SIDEREAL_YEAR
    The average number of days it takes for the sun to return to the same position against the fixed stellar background.
    static final double
    SOLAR_DAY
    The number of sidereal hours in one mean solar day.
    static final org.graalvm.shadowed.com.ibm.icu.impl.CalendarAstronomer.SolarLongitude
    SUMMER_SOLSTICE
    Constant representing the summer solstice.
    static final double
    SYNODIC_MONTH
    The average number of solar days from one new moon to the next.
    static final double
    TROPICAL_YEAR
    The average number number of days between successive vernal equinoxes.
    static final org.graalvm.shadowed.com.ibm.icu.impl.CalendarAstronomer.SolarLongitude
    VERNAL_EQUINOX
    Constant representing the vernal equinox.
    static final org.graalvm.shadowed.com.ibm.icu.impl.CalendarAstronomer.SolarLongitude
    WINTER_SOLSTICE
    Constant representing the winter solstice.

  • Constructor Summary

    Constructors
    Constructor
    Description
    CalendarAstronomer()
    Construct a new CalendarAstronomer object that is initialized to the current date and time.
    CalendarAstronomer(double longitude, double latitude)
    Construct a new CalendarAstronomer object with the given latitude and longitude.
    CalendarAstronomer(long aTime)
    Construct a new CalendarAstronomer object that is initialized to the specified time.
    CalendarAstronomer(Date d)
    Construct a new CalendarAstronomer object that is initialized to the specified date and time.

  • Method Summary

    Modifier and Type
    Method
    Description
    final CalendarAstronomer.Equatorial
    eclipticToEquatorial(double eclipLong)
    Convert from ecliptic longitude to equatorial coordinates.
    final CalendarAstronomer.Equatorial
    eclipticToEquatorial(double eclipLong, double eclipLat)
    Convert from ecliptic to equatorial coordinates.
    final CalendarAstronomer.Equatorial
    eclipticToEquatorial(CalendarAstronomer.Ecliptic ecliptic)
    Convert from ecliptic to equatorial coordinates.
    CalendarAstronomer.Horizon
    eclipticToHorizon(double eclipLong)
     
    Date
    getDate()
    Get the current time of this CalendarAstronomer object, represented as a Date object.
    double
    getGreenwichSidereal()
    Returns the current Greenwich sidereal time, measured in hours
    double
    getJulianCentury()
    Return this object's time expressed in julian centuries: the number of centuries after 1/1/1900 AD, 12:00 GMT
    double
    getJulianDay()
    Get the current time of this CalendarAstronomer object, expressed as a "julian day number", which is the number of elapsed days since 1/1/4713 BC (Julian), 12:00 GMT.
    double
    getLocalSidereal()
    Returns the current local sidereal time, measured in hours
    double
    getMoonAge()
    The "age" of the moon at the time specified in this object.
    double
    getMoonPhase()
    Calculate the phase of the moon at the time set in this object.
    CalendarAstronomer.Equatorial
    getMoonPosition()
    The position of the moon at the time set on this object, in equatorial coordinates.
    long
    getMoonRiseSet(boolean rise)
    Returns the time (GMT) of sunrise or sunset on the local date to which this calendar is currently set.
    long
    getMoonTime(double desired, boolean next)
    Find the next or previous time at which the Moon's ecliptic longitude will have the desired value.
    long
    getMoonTime(org.graalvm.shadowed.com.ibm.icu.impl.CalendarAstronomer.MoonAge desired, boolean next)
    Find the next or previous time at which the moon will be in the desired phase.
    double
    getSunLongitude()
    The longitude of the sun at the time specified by this object.
    CalendarAstronomer.Equatorial
    getSunPosition()
    The position of the sun at this object's current date and time, in equatorial coordinates.
    long
    getSunRiseSet(boolean rise)
    Returns the time (GMT) of sunrise or sunset on the local date to which this calendar is currently set.
    long
    getSunTime(double desired, boolean next)
    Find the next time at which the sun's ecliptic longitude will have the desired value.
    long
    getSunTime(org.graalvm.shadowed.com.ibm.icu.impl.CalendarAstronomer.SolarLongitude desired, boolean next)
    Find the next time at which the sun's ecliptic longitude will have the desired value.
    long
    getTime()
    Get the current time of this CalendarAstronomer object, represented as the number of milliseconds since 1/1/1970 AD 0:00 GMT (Gregorian).
    String
    local(long localMillis)
     
    void
    setDate(Date date)
    Set the current date and time of this CalendarAstronomer object.
    void
    setJulianDay(double jdn)
    Set the current date and time of this CalendarAstronomer object.
    void
    setTime(long aTime)
    Set the current date and time of this CalendarAstronomer object.

    Methods inherited from class java.lang.Object

    clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

  • Field Details

    • SIDEREAL_DAY

      public static final double SIDEREAL_DAY
      The number of standard hours in one sidereal day. Approximately 24.93.
      See Also:

    • SOLAR_DAY

      public static final double SOLAR_DAY
      The number of sidereal hours in one mean solar day. Approximately 24.07.
      See Also:

    • SYNODIC_MONTH

      public static final double SYNODIC_MONTH
      The average number of solar days from one new moon to the next. This is the time it takes for the moon to return the same ecliptic longitude as the sun. It is longer than the sidereal month because the sun's longitude increases during the year due to the revolution of the earth around the sun. Approximately 29.53.
      See Also:

    • SIDEREAL_MONTH

      public static final double SIDEREAL_MONTH
      The average number of days it takes for the moon to return to the same ecliptic longitude relative to the stellar background. This is referred to as the sidereal month. It is shorter than the synodic month due to the revolution of the earth around the sun. Approximately 27.32.
      See Also:

    • TROPICAL_YEAR

      public static final double TROPICAL_YEAR
      The average number number of days between successive vernal equinoxes. Due to the precession of the earth's axis, this is not precisely the same as the sidereal year. Approximately 365.24
      See Also:

    • SIDEREAL_YEAR

      public static final double SIDEREAL_YEAR
      The average number of days it takes for the sun to return to the same position against the fixed stellar background. This is the duration of one orbit of the earth about the sun as it would appear to an outside observer. Due to the precession of the earth's axis, this is not precisely the same as the tropical year. Approximately 365.25.
      See Also:

    • SECOND_MS

      public static final int SECOND_MS
      The number of milliseconds in one second.
      See Also:

    • MINUTE_MS

      public static final int MINUTE_MS
      The number of milliseconds in one minute.
      See Also:

    • HOUR_MS

      public static final int HOUR_MS
      The number of milliseconds in one hour.
      See Also:

    • DAY_MS

      public static final long DAY_MS
      The number of milliseconds in one day.
      See Also:

    • JULIAN_EPOCH_MS

      public static final long JULIAN_EPOCH_MS
      The start of the julian day numbering scheme used by astronomers, which is 1/1/4713 BC (Julian), 12:00 GMT. This is given as the number of milliseconds since 1/1/1970 AD (Gregorian), a negative number. Note that julian day numbers and the Julian calendar are not the same thing. Also note that julian days start at noon, not midnight.
      See Also:

    • VERNAL_EQUINOX

      public static final org.graalvm.shadowed.com.ibm.icu.impl.CalendarAstronomer.SolarLongitude VERNAL_EQUINOX
      Constant representing the vernal equinox. For use with getSunTime. Note: In this case, "vernal" refers to the northern hemisphere's seasons.

    • SUMMER_SOLSTICE

      public static final org.graalvm.shadowed.com.ibm.icu.impl.CalendarAstronomer.SolarLongitude SUMMER_SOLSTICE
      Constant representing the summer solstice. For use with getSunTime. Note: In this case, "summer" refers to the northern hemisphere's seasons.

    • AUTUMN_EQUINOX

      public static final org.graalvm.shadowed.com.ibm.icu.impl.CalendarAstronomer.SolarLongitude AUTUMN_EQUINOX
      Constant representing the autumnal equinox. For use with getSunTime. Note: In this case, "autumn" refers to the northern hemisphere's seasons.

    • WINTER_SOLSTICE

      public static final org.graalvm.shadowed.com.ibm.icu.impl.CalendarAstronomer.SolarLongitude WINTER_SOLSTICE
      Constant representing the winter solstice. For use with getSunTime. Note: In this case, "winter" refers to the northern hemisphere's seasons.

    • NEW_MOON

      public static final org.graalvm.shadowed.com.ibm.icu.impl.CalendarAstronomer.MoonAge NEW_MOON
      Constant representing a new moon. For use with getMoonTime

    • FIRST_QUARTER

      public static final org.graalvm.shadowed.com.ibm.icu.impl.CalendarAstronomer.MoonAge FIRST_QUARTER
      Constant representing the moon's first quarter. For use with getMoonTime

    • FULL_MOON

      public static final org.graalvm.shadowed.com.ibm.icu.impl.CalendarAstronomer.MoonAge FULL_MOON
      Constant representing a full moon. For use with getMoonTime

    • LAST_QUARTER

      public static final org.graalvm.shadowed.com.ibm.icu.impl.CalendarAstronomer.MoonAge LAST_QUARTER
      Constant representing the moon's last quarter. For use with getMoonTime

  • Constructor Details

    • CalendarAstronomer

      public CalendarAstronomer()
      Construct a new CalendarAstronomer object that is initialized to the current date and time.

    • CalendarAstronomer

      public CalendarAstronomer(Date d)
      Construct a new CalendarAstronomer object that is initialized to the specified date and time.

    • CalendarAstronomer

      public CalendarAstronomer(long aTime)
      Construct a new CalendarAstronomer object that is initialized to the specified time. The time is expressed as a number of milliseconds since January 1, 1970 AD (Gregorian).
      See Also:

    • CalendarAstronomer

      public CalendarAstronomer(double longitude, double latitude)
      Construct a new CalendarAstronomer object with the given latitude and longitude. The object's time is set to the current date and time.

      Parameters:
      longitude - The desired longitude, in degrees east of the Greenwich meridian.
      latitude - The desired latitude, in degrees. Positive values signify North, negative South.
      See Also:

  • Method Details

    • setTime

      public void setTime(long aTime)
      Set the current date and time of this CalendarAstronomer object. All astronomical calculations are performed based on this time setting.
      Parameters:
      aTime - the date and time, expressed as the number of milliseconds since 1/1/1970 0:00 GMT (Gregorian).
      See Also:

    • setDate

      public void setDate(Date date)
      Set the current date and time of this CalendarAstronomer object. All astronomical calculations are performed based on this time setting.
      Parameters:
      date - the time and date, expressed as a Date object.
      See Also:

    • setJulianDay

      public void setJulianDay(double jdn)
      Set the current date and time of this CalendarAstronomer object. All astronomical calculations are performed based on this time setting.
      Parameters:
      jdn - the desired time, expressed as a "julian day number", which is the number of elapsed days since 1/1/4713 BC (Julian), 12:00 GMT. Note that julian day numbers start at noon. To get the jdn for the corresponding midnight, subtract 0.5.
      See Also:

    • getTime

      public long getTime()
      Get the current time of this CalendarAstronomer object, represented as the number of milliseconds since 1/1/1970 AD 0:00 GMT (Gregorian).
      See Also:

    • getDate

      public Date getDate()
      Get the current time of this CalendarAstronomer object, represented as a Date object.
      See Also:

    • getJulianDay

      public double getJulianDay()
      Get the current time of this CalendarAstronomer object, expressed as a "julian day number", which is the number of elapsed days since 1/1/4713 BC (Julian), 12:00 GMT.
      See Also:

    • getJulianCentury

      public double getJulianCentury()
      Return this object's time expressed in julian centuries: the number of centuries after 1/1/1900 AD, 12:00 GMT
      See Also:

    • getGreenwichSidereal

      public double getGreenwichSidereal()
      Returns the current Greenwich sidereal time, measured in hours

    • getLocalSidereal

      public double getLocalSidereal()
      Returns the current local sidereal time, measured in hours

    • eclipticToEquatorial

      public final CalendarAstronomer.Equatorial eclipticToEquatorial(CalendarAstronomer.Ecliptic ecliptic)
      Convert from ecliptic to equatorial coordinates.
      Parameters:
      ecliptic - A point in the sky in ecliptic coordinates.
      Returns:
      The corresponding point in equatorial coordinates.

    • eclipticToEquatorial

      public final CalendarAstronomer.Equatorial eclipticToEquatorial(double eclipLong, double eclipLat)
      Convert from ecliptic to equatorial coordinates.
      Parameters:
      eclipLong - The ecliptic longitude
      eclipLat - The ecliptic latitude
      Returns:
      The corresponding point in equatorial coordinates.

    • eclipticToEquatorial

      public final CalendarAstronomer.Equatorial eclipticToEquatorial(double eclipLong)
      Convert from ecliptic longitude to equatorial coordinates.
      Parameters:
      eclipLong - The ecliptic longitude
      Returns:
      The corresponding point in equatorial coordinates.

    • eclipticToHorizon

      public CalendarAstronomer.Horizon eclipticToHorizon(double eclipLong)

    • getSunLongitude

      public double getSunLongitude()
      The longitude of the sun at the time specified by this object. The longitude is measured in radians along the ecliptic from the "first point of Aries," the point at which the ecliptic crosses the earth's equatorial plane at the vernal equinox.

      Currently, this method uses an approximation of the two-body Kepler's equation for the earth and the sun. It does not take into account the perturbations caused by the other planets, the moon, etc.

    • getSunPosition

      public CalendarAstronomer.Equatorial getSunPosition()
      The position of the sun at this object's current date and time, in equatorial coordinates.

    • getSunTime

      public long getSunTime(double desired, boolean next)
      Find the next time at which the sun's ecliptic longitude will have the desired value.

    • getSunTime

      public long getSunTime(org.graalvm.shadowed.com.ibm.icu.impl.CalendarAstronomer.SolarLongitude desired, boolean next)
      Find the next time at which the sun's ecliptic longitude will have the desired value.

    • getSunRiseSet

      public long getSunRiseSet(boolean rise)
      Returns the time (GMT) of sunrise or sunset on the local date to which this calendar is currently set. NOTE: This method only works well if this object is set to a time near local noon. Because of variations between the local official time zone and the geographic longitude, the computation can flop over into an adjacent day if this object is set to a time near local midnight.

    • getMoonPosition

      public CalendarAstronomer.Equatorial getMoonPosition()
      The position of the moon at the time set on this object, in equatorial coordinates.

    • getMoonAge

      public double getMoonAge()
      The "age" of the moon at the time specified in this object. This is really the angle between the current ecliptic longitudes of the sun and the moon, measured in radians.
      See Also:

    • getMoonPhase

      public double getMoonPhase()
      Calculate the phase of the moon at the time set in this object. The returned phase is a double in the range 0 invalid input: '<'= phase invalid input: '<' 1, interpreted as follows:
      • 0.00: New moon
      • 0.25: First quarter
      • 0.50: Full moon
      • 0.75: Last quarter
      See Also:

    • getMoonTime

      public long getMoonTime(double desired, boolean next)
      Find the next or previous time at which the Moon's ecliptic longitude will have the desired value.

      Parameters:
      desired - The desired longitude.
      next - true if the next occurrance of the phase is desired, false for the previous occurrance.

    • getMoonTime

      public long getMoonTime(org.graalvm.shadowed.com.ibm.icu.impl.CalendarAstronomer.MoonAge desired, boolean next)
      Find the next or previous time at which the moon will be in the desired phase.

      Parameters:
      desired - The desired phase of the moon.
      next - true if the next occurrance of the phase is desired, false for the previous occurrance.

    • getMoonRiseSet

      public long getMoonRiseSet(boolean rise)
      Returns the time (GMT) of sunrise or sunset on the local date to which this calendar is currently set.

    • local

      public String local(long localMillis)