Defining the precise time of observation, and support for all relevant astronomical timescales, such as UT1, UTC, TAI, GPS, TT, TDB, TCG, TCB. More...

Classes
class	supernovas::Calendar
	Type of calendar used for representing dates, such as Gregorian, Roman, or astronomical. More...
class	supernovas::CalendarDate
	A time specified in a specific type of calendar (Gregorian, Roman, or astronomical). More...
class	supernovas::Time
	Precise astronomical time specification, supporting all relevant astronomical timescales (UT1, UTC, TAI, GPS, TT, TDB, TCG, and TCB). More...

Macros
#define	NOVAS_GPS_TO_TAI 19.0
	[s] TAI - GPS time offset
#define	NOVAS_JD_MJD0 2400000.5
	[day] Julian date at which the Modified Julian Date (MJD) is zero
#define	NOVAS_JD_START_GREGORIAN 2299160.5
	[day] The Julian day the Gregorian calendar was introduced in 15 October 1582.
#define	NOVAS_TAI_TO_TT 32.184
	[s] TT - TAI time offset

Enumerations
enum	novas_timescale { NOVAS_TCB = 0 , NOVAS_TDB , NOVAS_TCG , NOVAS_TT , NOVAS_TAI , NOVAS_GPS , NOVAS_UTC , NOVAS_UT1 }
	Constants to reference various astronomical timescales used. More...

Functions
const Time &	supernovas::AstrometricPosition::emit_time () const
	Returns the time at which the observed light was emitted from this position, that is antedated from the time of observation by the time it takes for light to travel to the observer.
enum novas_timescale	novas_timescale_for_string (const char *restrict str)
	Returns the timescale constant for a string that denotes the timescale in with a standard abbreviation (case insensitive).
Time	supernovas::AstrometricPosition::obs_time () const
	Returns the reference time at which this position was observed by an observer at the reference location.
Time	supernovas::Source::rises_above (const Angle &el, const Frame &frame, RefractionModel ref=NULL, const Weather &weather=Weather::standard()) const
	Returns the time when the source rises above the specified elevation next for an observer located on or near Earth's surface, or else std::nullopt if the observer is not near Earth's surface.
Time	supernovas::Source::sets_below (const Angle &el, const Frame &frame, RefractionModel ref=NULL, const Weather &weather=Weather::standard()) const
	Returns the time when the source sets below the specified elevation next for an observer located on or near Earth's surface, or else std::nullopt if the observer is not near Earth's surface.
Time	supernovas::Source::transits_in (const Frame &frame) const
	Returns the time when the source transits for an observer located on or near Earth's surface, or else std::nullopt if the observer is not near Earth's surface.
double	tt2tdb_fp (double jd_tt, double limit)
	Returns the TDB-TT time difference with flexible precision.

Detailed Description

Defining the precise time of observation, and support for all relevant astronomical timescales, such as UT1, UTC, TAI, GPS, TT, TDB, TCG, TCB.

Macro Definition Documentation

◆ NOVAS_GPS_TO_TAI

#define NOVAS_GPS_TO_TAI 19.0

[s] TAI - GPS time offset

◆ NOVAS_JD_MJD0

#define NOVAS_JD_MJD0 2400000.5

[day] Julian date at which the Modified Julian Date (MJD) is zero

Referenced by supernovas::Time::from_mjd(), supernovas::CalendarDate::mjd(), supernovas::Ecliptic::mjd(), supernovas::Equinox::mjd(), and supernovas::Time::mjd().

◆ NOVAS_JD_START_GREGORIAN

#define NOVAS_JD_START_GREGORIAN 2299160.5

[day] The Julian day the Gregorian calendar was introduced in 15 October 1582.

The day prior to that was 4 October 1582 in the Julian Calendar.

Referenced by novas_day_of_year(), novas_jd_from_date(), and novas_jd_to_date().

◆ NOVAS_TAI_TO_TT

#define NOVAS_TAI_TO_TT 32.184

[s] TT - TAI time offset

Referenced by get_utc_to_tt().

Enumeration Type Documentation

◆ novas_timescale

enum novas_timescale

Constants to reference various astronomical timescales used.

Since: 1.1

See also: novas_set_time(), novas_get_time(), novas_diff_time(), novas_clock_skew(), NOVAS_TIMESCALES; timescale.c

Enumerator
NOVAS_TCB	Barycentric Coordinate Time (TCB).
NOVAS_TDB	Barycentric Dynamical Time (TDB).
NOVAS_TCG	Geocentric Coordinate Time (TCG).
NOVAS_TT	Terrestrial Time (TT).
NOVAS_TAI	Innternational Atomic Time (TAI).
NOVAS_GPS	GPS Time.
NOVAS_UTC	Universal Coordinated Time (UTC).
NOVAS_UT1	UT1 earth rotation time, based on the measured Earth orientation parameters published in IERS Bulletin A.

Function Documentation

◆ emit_time()

const Time & supernovas::AstrometricPosition::emit_time ( ) const

Returns the time at which the observed light was emitted from this position, that is antedated from the time of observation by the time it takes for light to travel to the observer.

Returns: the time at which observed light was emitted from this position.

See also: obs_time()

◆ novas_timescale_for_string()

enum novas_timescale novas_timescale_for_string ( const char *restrict str )

Returns the timescale constant for a string that denotes the timescale in with a standard abbreviation (case insensitive).

The following values are recognised: "UTC", "UT", "UT0", "UT1", "GMT", "TAI", "GPS", "TT", "ET", "TCG", "TCB", and "TDB".

Parameters

str	String specifying an astronomical timescale

Returns: The SuperNOVAS timescale constant (<=0), or else -1 if the string was NULL, empty, or could not be matched to a timescale value (errno will be set to EINVAL also).

Since: 1.3

Author: Attila Kovacs

See also: novas_parse_timescale(), novas_set_str_time(), novas_print_timescale()

References NOVAS_GPS, NOVAS_TAI, NOVAS_TCB, NOVAS_TCG, NOVAS_TDB, NOVAS_TT, NOVAS_UT1, and NOVAS_UTC.

Referenced by novas_parse_timescale().

◆ obs_time()

Time supernovas::AstrometricPosition::obs_time ( ) const

Returns the reference time at which this position was observed by an observer at the reference location.

Returns: the time at which this position is defined.

See also: emit_time(), reference()

References supernovas::Constant::c, supernovas::Position::distance(), supernovas::Validating::is_valid(), and supernovas::Coordinate::m().

Referenced by as_equatorial(), and referenced_to().

◆ rises_above()

Time supernovas::Source::rises_above	(	const Angle &	el,
		const Frame &	frame,
		RefractionModel	ref = NULL,
		const Weather &	weather = Weather::standard() ) const

Returns the time when the source rises above the specified elevation next for an observer located on or near Earth's surface, or else std::nullopt if the observer is not near Earth's surface.

The returned value may also be NAN if the source does not cross the specified elevation theshold within a day of the specified time of observation.

Parameters

el	elevation threshold angle
Observing frames	observing frame (observer location and the lower bound for the returned time).
ref	atmospheric refraction model to assume
weather	local weather parameters for the refraction calculation

Returns: the next time the source rises above the specified elevation after the frame's observing time. It may be NAN if the source does not cross (rises above or sets below) the elevation threshold within a day of the specified time of observation. For observers non near Earth's surface, Time::undefined() will be returned.

See also: sets_below(), transits_in()

References supernovas::Frame::_novas_frame(), _object, supernovas::Angle::deg(), supernovas::Frame::eop(), supernovas::Validating::is_valid(), and novas_rises_above().

◆ sets_below()

Time supernovas::Source::sets_below	(	const Angle &	el,
		const Frame &	frame,
		RefractionModel	ref = NULL,
		const Weather &	weather = Weather::standard() ) const

Returns the time when the source sets below the specified elevation next for an observer located on or near Earth's surface, or else std::nullopt if the observer is not near Earth's surface.

The returned value may also be NAN if the source does not cross the specified elevation theshold within a day of the specified time of observation.

Parameters

el	elevation threshold angle
Observing frames	observing frame (observer location and the lower bound for the returned time).
ref	atmospheric refraction model to assume
weather	local weather parameters for the refraction calculation

Returns: the next time the source sets the specified elevation after the frame's observing time. It may be NAN if the source does not cross (rises above or sets below) the elevation threshold within a day of the specified time of observation. For observers not near Earth's surface, Time::undefined() will be returned.

See also: rises_above(), transits_in()

References supernovas::Frame::_novas_frame(), _object, supernovas::Angle::deg(), supernovas::Frame::eop(), supernovas::Validating::is_valid(), and novas_sets_below().

◆ transits_in()

Time supernovas::Source::transits_in ( const Frame & frame ) const

Returns the time when the source transits for an observer located on or near Earth's surface, or else std::nullopt if the observer is not near Earth's surface.

Parameters

Observing frames observing frame (observer location and the lower bound for the returned time).

Returns: the next time the source transits after the frame's observing time, or else Time::undefined() if the observer is not near Earth's surface .

See also: sets_below(), transits_in()

References supernovas::Frame::_novas_frame(), _object, supernovas::Frame::eop(), supernovas::Validating::is_valid(), and novas_transit_time().

◆ tt2tdb_fp()

double tt2tdb_fp	(	double	jd_tt,
		double	limit )

Returns the TDB-TT time difference with flexible precision.

This implementation uses the series expansion by Fairhead & Bretagnon 1990, terminating the terms at or below the specified limiting amplitude.

REFERENCES:

Fairhead, L., & Bretagnon, P. (1990) A&A, 229, 240

Parameters

jd_tt	[day] Terrestrial Time (TT) based Julian date, but Barycentric Dynamical Time (TDB)
limit	[us] Amplitude of limiting term to include in series. 0 or negative values will include all terms, producing the same result as tt2tdb_hp().

Returns: [s] TDB - TT time difference.

Since: 1.4

Author: Attila Kovacs

See also: tt2tdb_hp(), tt2tdb()

References NOVAS_JD_J2000.

Referenced by tt2tdb_hp().

Classes

Macros

Enumerations

Functions

Detailed Description

Macro Definition Documentation

◆ NOVAS_GPS_TO_TAI

◆ NOVAS_JD_MJD0

◆ NOVAS_JD_START_GREGORIAN

◆ NOVAS_TAI_TO_TT

Enumeration Type Documentation

◆ novas_timescale

Function Documentation

◆ emit_time()

◆ novas_timescale_for_string()

◆ obs_time()

◆ rises_above()

◆ sets_below()

◆ transits_in()

◆ tt2tdb_fp()