supernovas::HorizontalTrack Class Reference

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

#include <supernovas.h>

Inheritance diagram for supernovas::HorizontalTrack:

Public Member Functions
	HorizontalTrack (const Time &ref_time, const Interval &range, const ScalarEvolution &azimuth, const ScalarEvolution &elevation, const ScalarEvolution &distance=ScalarEvolution::stationary(Unit::Gpc), const ScalarEvolution &z=ScalarEvolution::undefined())
	Instantiates a short-term horizontal source trajectory on sky for a given reference time, time evolution, and time range of validity.
Horizontal	projected_at (const Time &time) const override
	Returns the momentary extrapolated horizontal coordinates (if valid), or else Horizontal::undefined() if the time is outside the range of validity.
Public Member Functions inherited from supernovas::Track< Horizontal >
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 HorizontalTrack	from_novas_track (const novas_track *track, const Interval &range)
	Instantiates a short-term trajectory estimate for a source in horizontal coordinates, which can be used to extrapolate the horizontal (Az/El) positions of the source around the specified reference time inside an interval of validity.
static const HorizontalTrack &	undefined ()
	Returns a reference to a static instance of a standard undefined horizontal track.

Additional Inherited Members
Protected Member Functions inherited from supernovas::Track< Horizontal >
	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 horizontal coordinates, using a local quadratic approximation around a time instant.

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

See also

Apparent::horizontal(), EquatorialTrack

Constructor & Destructor Documentation

HorizontalTrack()

supernovas::HorizontalTrack::HorizontalTrack	(	const Time &	ref_time,
		const Interval &	range,
		const ScalarEvolution &	azimuth,
		const ScalarEvolution &	elevation,
		const ScalarEvolution &	distance = ScalarEvolution::stationary(Unit::Gpc),
		const ScalarEvolution &	z = ScalarEvolution::undefined() )

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

Parameters

ref_time	astrometric reference time for which the data is defined.
range	time range of validity around the reference time for extrapolating.
azimuth	short-term time evolution of the azimuth coordinate.
elevation	short-term time evolution of the elevation 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(), EquatorialTrack::EquatorialTrack()

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

Member Function Documentation

from_novas_track()

HorizontalTrack supernovas::HorizontalTrack::from_novas_track ( const novas_track * track, const Interval & range )

static

Instantiates a short-term trajectory estimate for a source in horizontal coordinates, which can be used to extrapolate the horizontal (Az/El) 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:

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

Parameters

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

EquatorialTrack::from_novas_track()

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

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

projected_at()

Horizontal supernovas::HorizontalTrack::projected_at ( const Time & time ) const

overridevirtual

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

It is best practice to check on its validity before use, e.g. as:

Horizontal hor = track.projected_at(...);
if(!hor) {
  // Oops, not valid
  return;
}

Parameters

Time of observation and astronomical timescales

astrometric time for which we want the extrapolated value.

Returns

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

See also

EquatorialTrack::projected_at()

Implements supernovas::Track< Horizontal >.

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

undefined()

const HorizontalTrack & supernovas::HorizontalTrack::undefined ( )

static

Returns a reference to a static instance of a standard undefined horizontal track.

Returns

the reference to a standard undefined horizontal track.

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