| java.lang.Object
 com.ibm.icu.impl.CalendarAstronomer
| CalendarAstronomer | | public class CalendarAstronomer (Code) | | 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
CalendarAstronomer.setDate setDate ,
CalendarAstronomer.getDate 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
com.ibm.icu.util.IslamicCalendar and
com.ibm.icu.util.ChineseCalendar .
author:
Laura Werner
author:
Alan Liu |
| Inner Class :final public static class Ecliptic | |
| Inner Class :final public static class Equatorial | |
| Inner Class :final public static class Horizon | |
| Field Summary | |
| final public static SolarLongitude | AUTUMN_EQUINOX
Constant representing the autumnal equinox. | | final public static long | DAY_MS
The number of milliseconds in one day. | | final static long | EPOCH_2000_MS
Milliseconds value for 0.0 January 2000 AD. | | final public static MoonAge | FIRST_QUARTER
Constant representing the moon's first quarter. | | final public static MoonAge | FULL_MOON
Constant representing a full moon. | | final public static int | HOUR_MS
The number of milliseconds in one hour. | | final static double | JD_EPOCH
| | final public static 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. | | final public static MoonAge | LAST_QUARTER
Constant representing the moon's last quarter. | | final public static int | MINUTE_MS
The number of milliseconds in one minute. | | final public static MoonAge | NEW_MOON
Constant representing a new moon. | | final public static int | SECOND_MS
The number of milliseconds in one second. | | final public static double | SIDEREAL_DAY
The number of standard hours in one sidereal day. | | final public static 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. | | final public static double | SIDEREAL_YEAR
The average number of days it takes
for the sun to return to the same position against the fixed stellar
background. | | final public static double | SOLAR_DAY
The number of sidereal hours in one mean solar day. | | final public static SolarLongitude | SUMMER_SOLSTICE
Constant representing the summer solstice. | | final static double | SUN_E
| | final static double | SUN_ETA_G
| | final static double | SUN_OMEGA_G
| | final public static double | SYNODIC_MONTH
The average number of solar days from one new moon to the next. | | final public static double | TROPICAL_YEAR
The average number number of days between successive vernal equinoxes. | | final public static SolarLongitude | VERNAL_EQUINOX
Constant representing the vernal equinox.
For use with
CalendarAstronomer.getSunTime(SolarLongitude,boolean) getSunTime . | | final public static SolarLongitude | WINTER_SOLSTICE
Constant representing the winter solstice. | | final static double | moonA
| | final static double | moonE
| | final static double | moonI
| | final static double | moonL0
| | final static double | moonN0
| | final static double | moonP0
| | final static double | moonPi
| | final static double | moonT0
|
| Constructor Summary | |
| public | CalendarAstronomer()
Construct a new CalendarAstronomer object that is initialized to
the current date and time. | | public | CalendarAstronomer(Date d)
Construct a new CalendarAstronomer object that is initialized to
the specified date and time. | | public | CalendarAstronomer(long aTime)
Construct a new CalendarAstronomer object that is initialized to
the specified time. | | public | CalendarAstronomer(double longitude, double latitude)
Construct a new CalendarAstronomer object with the given
latitude and longitude. |
| Method Summary | |
| final public Equatorial | eclipticToEquatorial(Ecliptic ecliptic)
Convert from ecliptic to equatorial coordinates.
Parameters:
ecliptic - A point in the sky in ecliptic coordinates. | | final public Equatorial | eclipticToEquatorial(double eclipLong, double eclipLat)
Convert from ecliptic to equatorial coordinates. | | final public Equatorial | eclipticToEquatorial(double eclipLong)
Convert from ecliptic longitude to equatorial coordinates. | | public Horizon | eclipticToHorizon(double eclipLong)
| | public Date | getDate()
Get the current time of this CalendarAstronomer object,
represented as a Date object. | | public double | getGreenwichSidereal()
| | public double | getJulianCentury()
| | 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. | | public double | getLocalSidereal()
| | public double | getMoonAge()
The "age" of the moon at the time specified in this object. | | public double | getMoonPhase()
Calculate the phase of the moon at the time set in this object. | | public Equatorial | getMoonPosition()
The position of the moon at the time set on this
object, in equatorial coordinates. | | public long | getMoonRiseSet(boolean rise)
Returns the time (GMT) of sunrise or sunset on the local date to which
this calendar is currently set. | | 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. | | public long | getMoonTime(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.
Parameters:
next - true if the next occurrance of the phaseis desired, false for the previous occurrance. | | 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. | | double[] | getSunLongitude(double julianDay)
TODO Make this public when the entire class is package-private. | | public Equatorial | getSunPosition()
The position of the sun at this object's current date and time,
in equatorial coordinates. | | 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. | | public long | getSunTime(double desired, boolean next)
Find the next time at which the sun's ecliptic longitude will have
the desired value. | | public long | getSunTime(SolarLongitude desired, boolean next)
Find the next time at which the sun's ecliptic longitude will have
the desired value. | | 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). | | public String | local(long localMillis)
| | public void | setDate(Date date)
Set the current date and time of this CalendarAstronomer object. | | public void | setJulianDay(double jdn)
Set the current date and time of this CalendarAstronomer object. | | public void | setTime(long aTime)
Set the current date and time of this CalendarAstronomer object. |
| DAY_MS | | final public static long DAY_MS(Code) | | The number of milliseconds in one day.
|
| EPOCH_2000_MS | | final static long EPOCH_2000_MS(Code) | | Milliseconds value for 0.0 January 2000 AD.
|
| HOUR_MS | | final public static int HOUR_MS(Code) | | The number of milliseconds in one hour.
|
| JD_EPOCH | | final static double JD_EPOCH(Code) | | |
| JULIAN_EPOCH_MS | | final public static long JULIAN_EPOCH_MS(Code) | | 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.
|
| MINUTE_MS | | final public static int MINUTE_MS(Code) | | The number of milliseconds in one minute.
|
| SECOND_MS | | final public static int SECOND_MS(Code) | | The number of milliseconds in one second.
|
| SIDEREAL_DAY | | final public static double SIDEREAL_DAY(Code) | | The number of standard hours in one sidereal day.
Approximately 24.93.
|
| SIDEREAL_MONTH | | final public static double SIDEREAL_MONTH(Code) | | 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: CalendarAstronomer.SYNODIC_MONTH |
| SIDEREAL_YEAR | | final public static double SIDEREAL_YEAR(Code) | | 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: CalendarAstronomer.TROPICAL_YEAR |
| SOLAR_DAY | | final public static double SOLAR_DAY(Code) | | The number of sidereal hours in one mean solar day.
Approximately 24.07.
|
| SUN_E | | final static double SUN_E(Code) | | |
| SUN_ETA_G | | final static double SUN_ETA_G(Code) | | |
| SUN_OMEGA_G | | final static double SUN_OMEGA_G(Code) | | |
| SYNODIC_MONTH | | final public static double SYNODIC_MONTH(Code) | | 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: CalendarAstronomer.SIDEREAL_MONTH |
| TROPICAL_YEAR | | final public static double TROPICAL_YEAR(Code) | | 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: CalendarAstronomer.SIDEREAL_YEAR |
| moonA | | final static double moonA(Code) | | |
| moonE | | final static double moonE(Code) | | |
| moonI | | final static double moonI(Code) | | |
| moonL0 | | final static double moonL0(Code) | | |
| moonN0 | | final static double moonN0(Code) | | |
| moonP0 | | final static double moonP0(Code) | | |
| moonPi | | final static double moonPi(Code) | | |
| moonT0 | | final static double moonT0(Code) | | |
| CalendarAstronomer | | public CalendarAstronomer()(Code) | | Construct a new CalendarAstronomer object that is initialized to
the current date and time.
|
| CalendarAstronomer | | public CalendarAstronomer(Date d)(Code) | | Construct a new CalendarAstronomer object that is initialized to
the specified date and time.
|
| CalendarAstronomer | | public CalendarAstronomer(long aTime)(Code) | | 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: java.util.Date.getTime |
| CalendarAstronomer | | public CalendarAstronomer(double longitude, double latitude)(Code) | | 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 ofthe Greenwich meridian.
Parameters:
latitude - The desired latitude, in degrees. Positivevalues signify North, negative South.
See Also: java.util.Date.getTime |
| eclipticToEquatorial | | final public Equatorial eclipticToEquatorial(Ecliptic ecliptic)(Code) | | Convert from ecliptic to equatorial coordinates.
Parameters:
ecliptic - A point in the sky in ecliptic coordinates. The corresponding point in equatorial coordinates. |
| eclipticToEquatorial | | final public Equatorial eclipticToEquatorial(double eclipLong, double eclipLat)(Code) | | Convert from ecliptic to equatorial coordinates.
Parameters:
eclipLong - The ecliptic longitude
Parameters:
eclipLat - The ecliptic latitude The corresponding point in equatorial coordinates. |
| eclipticToEquatorial | | final public Equatorial eclipticToEquatorial(double eclipLong)(Code) | | Convert from ecliptic longitude to equatorial coordinates.
Parameters:
eclipLong - The ecliptic longitude The corresponding point in equatorial coordinates. |
| eclipticToHorizon | | public Horizon eclipticToHorizon(double eclipLong)(Code) | | |
| getGreenwichSidereal | | public double getGreenwichSidereal()(Code) | | Returns the current Greenwich sidereal time, measured in hours
|
| getJulianCentury | | public double getJulianCentury()(Code) | | Return this object's time expressed in julian centuries:
the number of centuries after 1/1/1900 AD, 12:00 GMT
See Also: CalendarAstronomer.getJulianDay |
| getLocalSidereal | | public double getLocalSidereal()(Code) | | Returns the current local sidereal time, measured in hours
|
| getMoonAge | | public double getMoonAge()(Code) | | 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: CalendarAstronomer.getMoonPhase |
| getMoonPhase | | public double getMoonPhase()(Code) | | Calculate the phase of the moon at the time set in this object.
The returned phase is a double in the range
0 <= phase < 1, interpreted as follows:
- 0.00: New moon
- 0.25: First quarter
- 0.50: Full moon
- 0.75: Last quarter
See Also: CalendarAstronomer.getMoonAge |
| getMoonPosition | | public Equatorial getMoonPosition()(Code) | | The position of the moon at the time set on this
object, in equatorial coordinates.
|
| getMoonRiseSet | | public long getMoonRiseSet(boolean rise)(Code) | | Returns the time (GMT) of sunrise or sunset on the local date to which
this calendar is currently set.
|
| getMoonTime | | public long getMoonTime(double desired, boolean next)(Code) | | Find the next or previous time at which the Moon's ecliptic
longitude will have the desired value.
Parameters:
desired - The desired longitude.
Parameters:
next - true if the next occurrance of the phaseis desired, false for the previous occurrance. |
| getMoonTime | | public long getMoonTime(MoonAge desired, boolean next)(Code) | | Find the next or previous time at which the moon will be in the
desired phase.
Parameters:
desired - The desired phase of the moon.
Parameters:
next - true if the next occurrance of the phaseis desired, false for the previous occurrance. |
| getSunLongitude | | public double getSunLongitude()(Code) | | 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.
|
| getSunLongitude | | double[] getSunLongitude(double julianDay)(Code) | | TODO Make this public when the entire class is package-private.
|
| getSunPosition | | public Equatorial getSunPosition()(Code) | | The position of the sun at this object's current date and time,
in equatorial coordinates.
|
| getSunRiseSet | | public long getSunRiseSet(boolean rise)(Code) | | 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.
|
| getSunTime | | public long getSunTime(double desired, boolean next)(Code) | | Find the next time at which the sun's ecliptic longitude will have
the desired value.
|
| getSunTime | | public long getSunTime(SolarLongitude desired, boolean next)(Code) | | Find the next time at which the sun's ecliptic longitude will have
the desired value.
|
| setDate | | public void setDate(Date date)(Code) | | 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: CalendarAstronomer.setTime
See Also: CalendarAstronomer.getDate |
| setJulianDay | | public void setJulianDay(double jdn)(Code) | | 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 daynumbers start at noon. To get the jdn forthe corresponding midnight, subtract 0.5.
See Also: CalendarAstronomer.getJulianDay
See Also: CalendarAstronomer.JULIAN_EPOCH_MS |
| setTime | | public void setTime(long aTime)(Code) | | 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 since1/1/1970 0:00 GMT (Gregorian).
See Also: CalendarAstronomer.setDate
See Also: CalendarAstronomer.getTime |
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