supernovas::EquatorialTrack Class Reference

Approximate trajectory of a source in equatorial coordinates, using a local quadratic approximation around a time instant. More...

#include <supernovas.h>

Inheritance diagram for supernovas::EquatorialTrack:

Public Member Functions
	EquatorialTrack (const Equinox &system, const Time &ref_time, const Interval &range, const ScalarEvolution &ra, const ScalarEvolution &dec, const ScalarEvolution &distance=ScalarEvolution::stationary(Unit::Gpc), const ScalarEvolution &z=ScalarEvolution::undefined())
	Instantiates a short-term equatorial source trajectory on sky for a given reference time, time evolution, and time range of validity.
Equatorial	projected_at (const Time &time) const override
	Returns the momentary extrapolated equatorial coordinates (if valid), or else Equatorial::undefined() if the time is outside the range of validity.
Public Member Functions inherited from supernovas::Track< Equatorial >
Coordinate	distance_at (const Time &time) const
	Returns the momentary extrapolated distance (if valid), or else std::nullopt if the time is outside the range of validity.
const ScalarEvolution &	distance_evolution () const
	Returns the time evolution of radial distance in this trajectory.
bool	is_valid_at (const Time &time) const
	Checks if the trajectory provides valid extrapolated data at a given astrometric time.
Angle	latitude_at (const Time &time) const
	Returns the momentary extrapolated latitude angle (if valid), or else std::nullopt if the time is outside the range of validity.
const ScalarEvolution &	latitude_evolution () const
	Returns the latitudinal time evolution component of this trajectory.
Angle	longitude_at (const Time &time) const
	Returns the momentary extrapolated longitude angle (if valid), or else std::nullopt if the time is outside the range of validity.
const ScalarEvolution &	longitude_evolution () const
	Returns the longitudinal time evolution component of this trajectory.
ScalarVelocity	radial_velocity_at (const Time &time) const
	Returns the momentary extrapolated radial velocity (if valid), or else std::nullopt if the time is outside the range of validity.
const Interval &	range () const
	Returns the time range of validity for this trajectory.
double	redshift_at (const Time &time) const
	Returns the momentary extrapolated redshift measure (if valid), or else NAN if the time is outside the range of validity.
const ScalarEvolution &	redshift_evolution () const
	Returns the redshift evolution in this trajectory.
const Time &	reference_time () const
	Returns the astrometic time of reference, at which the (quadratic) trajectory has been defined.
Public Member Functions inherited from supernovas::Validating
bool	is_valid () const
	Returns the previously set 'valid' stae of the implementing instance.
	operator bool () const
	Objects that implement Validating can be used in conditionals directly, without explicitly calling is_valid().

Static Public Member Functions
static EquatorialTrack	from_novas_track (const Equinox &system, const novas_track *track, const Interval &range)
	Instantiates a short-term trajectory estimate for a source in equatorial coordinates, which can be used to extrapolate the equatorial (RA/Dec) positions of the source around the specified reference time inside an interval of validity.

Additional Inherited Members
Protected Member Functions inherited from supernovas::Track< Equatorial >
	Track ()
virtual	~Track ()
Coordinate	unchecked_distance (const Time &time) const
	Returns the momentary extrapolated distance, without checking if the requested time is inside the range of validity.
Angle	unchecked_latitude (const Time &time) const
	Returns the momentary extrapolated latitude angle, without checking if the requested time is inside the range of validity.
Angle	unchecked_longitude (const Time &time) const
	Returns the momentary extrapolated longitude angle, without checking if the requested time is inside the range of validity.
double	unchecked_redshift (const Time &time) const
	Returns the momentary extrapolated redshift, without checking if the requested time is inside the range of validity.
Protected Member Functions inherited from supernovas::Validating
	Validating ()
	dummy constructor;
Protected Attributes inherited from supernovas::Validating
bool	_valid = false
	the state variable.

Detailed Description

Approximate trajectory of a source in equatorial coordinates, using a local quadratic approximation around a time instant.

This may be used e.g., to control telescope drive systems in equatorial mounts, by providing instantaneous positions, rate, and acceletation along the R.A. and declination axes. Or, one may use the trajectory to obtain interpolated instantaneous R.A./Dec positions, distances, spectroscopic redshifts or radial velocities within the interval of validity, at very low computational cost.

See also

Apparent::equatorial(), HorizontalTrack

Constructor & Destructor Documentation

EquatorialTrack()

supernovas::EquatorialTrack::EquatorialTrack	(	const Equinox &	system,
		const Time &	ref_time,
		const Interval &	range,
		const ScalarEvolution &	ra,
		const ScalarEvolution &	dec,
		const ScalarEvolution &	distance = ScalarEvolution::stationary(Unit::Gpc),
		const ScalarEvolution &	z = ScalarEvolution::undefined() )

Instantiates a short-term equatorial source trajectory on sky for a given reference time, time evolution, and time range of validity.

The returned track may be invalid if the input parameters are invalid. As such it is best practice to check on its validity before use, e.g. as:

EquatorialTrack tr(...);
if(!tr) {
  // Oops, the track is not valid
  return;
}

Parameters

system	the equatorial coordinate system in which the trajectory is defined.
ref_time	astrometric reference time for which the data is defined.
range	time range of validity around the reference time for extrapolating.
ra	short-term time evolution of the right-ascention (R.A.) coordinate.
dec	short-term time evolution of the declination coordinate.
distance	(optional) short-term time evolution of distance (default: static at 1 Gpc).
z	(optional) time evolution of redshift, including gravitational effects. If it's kinetic only, then you can leave it undefined to let the distance evolution determine it automatically.

See also

from_novas_track(), HorizontalTrack::HorizontalTrackTrack()

References supernovas::Track< Equatorial >::Track(), supernovas::Validating::is_valid(), and supernovas::Track< Equatorial >::range().

Member Function Documentation

from_novas_track()

EquatorialTrack supernovas::EquatorialTrack::from_novas_track ( const Equinox & system, const novas_track * track, const Interval & range )

static

Instantiates a short-term trajectory estimate for a source in equatorial coordinates, which can be used to extrapolate the equatorial (RA/Dec) positions of the source around the specified reference time inside an interval of validity.

The returned track may be invalid if the input parameters are invalid. As such it is best practice to check on its validity before use, e.g. as:

EquatorialTrack tr = EquatorialTrack::from_novas_track(...);
if(!tr) {
  // Oops, the track is not valid
  return;
}

Parameters

system	equatorial coordinate system
track	Pointer to the C tajectory data structure
range	time range of validity around the reference time. Attempts to extrapolate outside this interval will produce invalid data.

See also

HorizontalTrack::from_novas_track()

References supernovas::Validating::is_valid(), and supernovas::Track< Equatorial >::range().

Referenced by supernovas::Source::equatorial_track().

projected_at()

Equatorial supernovas::EquatorialTrack::projected_at ( const Time & time ) const

overridevirtual

Returns the momentary extrapolated equatorial coordinates (if valid), or else Equatorial::undefined() if the time is outside the range of validity.

It is best practice to check the valifity of the returned value before using it, e.g. as:

Equatorial eq = track.projected_at(...);
if(!eq) {
  // Oops, we could not interpolate valid data
  return;
}

Parameters

Time of observation and astronomical timescales

astrometric time for which we want the extrapolated value.

Returns

the momentary extrapolated equatorial coordinates (if valid), or else std::nullopt.

See also

HorizontalTrack::projected_at()

Implements supernovas::Track< Equatorial >.

References supernovas::Validating::is_valid(), supernovas::Track< Equatorial >::is_valid_at(), supernovas::Track< Equatorial >::unchecked_latitude(), supernovas::Track< Equatorial >::unchecked_longitude(), and supernovas::Equatorial::undefined().