PrecessedGeocentric

class astropy.coordinates.PrecessedGeocentric(*args, copy=True, representation_type=None, differential_type=None, **kwargs)

Bases: BaseRADecFrame

A coordinate frame defined in a similar manner as GCRS, but precessed to a requested (mean) equinox. Note that this does not end up the same as regular GCRS even for J2000 equinox, because the GCRS orientation is fixed to that of ICRS, which is not quite the same as the dynamical J2000 orientation.

The frame attributes are listed under Other Parameters

Parameters:

dataBaseRepresentation subclass instance

A representation object or None to have no data (or use the coordinate component arguments, see below).

raAngle, optional, keyword-only

The RA for this object (dec must also be given and representation must be None).

decAngle, optional, keyword-only

The Declination for this object (ra must also be given and representation must be None).

distanceQuantity [:ref: ‘length’], optional, keyword-only

The Distance for this object along the line-of-sight. (representation must be None).

pm_ra_cosdecQuantity [:ref: ‘angular speed’], optional, keyword-only

The proper motion in Right Ascension (including the cos(dec) factor) for this object (pm_dec must also be given).

pm_decQuantity [:ref: ‘angular speed’], optional, keyword-only

The proper motion in Declination for this object (pm_ra_cosdec must also be given).

radial_velocityQuantity [:ref: ‘speed’], optional, keyword-only

The radial velocity of this object.

representation_typeBaseRepresentation subclass, str, optional

A representation class or string name of a representation class. This sets the expected input representation class, thereby changing the expected keyword arguments for the data passed in. For example, passing representation_type='cartesian' will make the classes expect position data with cartesian names, i.e. x, y, z in most cases unless overridden via frame_specific_representation_info. To see this frame’s names, check out <this frame>().representation_info.

differential_typeBaseDifferential subclass, str, dict, optional

A differential class or dictionary of differential classes (currently only a velocity differential with key ‘s’ is supported). This sets the expected input differential class, thereby changing the expected keyword arguments of the data passed in. For example, passing differential_type='cartesian' will make the classes expect velocity data with the argument names v_x, v_y, v_z unless overridden via frame_specific_representation_info. To see this frame’s names, check out <this frame>().representation_info.

copybool, optional

If True (default), make copies of the input coordinate arrays. Can only be passed in as a keyword argument.

Other Parameters:

equinoxTime

The (mean) equinox to precess the coordinates to.

obstimeTime

The time at which the observation is taken. Used for determining the position of the Earth.

obsgeolocCartesianRepresentation, Quantity

The position of the observer relative to the center-of-mass of the Earth, oriented the same as BCRS/ICRS. Either [0, 0, 0], CartesianRepresentation, or proper input for one, i.e., a Quantity with shape (3, …) and length units. Defaults to [0, 0, 0], meaning “true” Geocentric.

obsgeovelCartesianRepresentation, Quantity

The velocity of the observer relative to the center-of-mass of the Earth, oriented the same as BCRS/ICRS. Either 0, CartesianRepresentation, or proper input for one, i.e., a Quantity with shape (3, …) and velocity units. Defaults to [0, 0, 0], meaning “true” Geocentric.

Attributes Summary

default_differential	Default representation for differential data (e.g., velocity)
default_representation	Default representation for position data
equinox
frame_attributes
frame_specific_representation_info	Mapping for frame-specific component names
name
obsgeoloc
obsgeovel
obstime

Attributes Documentation

default_differential

Default representation for differential data (e.g., velocity)

default_representation

Default representation for position data

equinox = <Time object: scale='tt' format='jyear_str' value=J2000.000>

frame_attributes = {'equinox': <astropy.coordinates.attributes.TimeAttribute object>, 'obsgeoloc': <astropy.coordinates.attributes.CartesianRepresentationAttribute object>, 'obsgeovel': <astropy.coordinates.attributes.CartesianRepresentationAttribute object>, 'obstime': <astropy.coordinates.attributes.TimeAttribute object>}

frame_specific_representation_info

Mapping for frame-specific component names

name = 'precessedgeocentric'

obsgeoloc = <CartesianRepresentation (x, y, z) in m     (0., 0., 0.)>

obsgeovel = <CartesianRepresentation (x, y, z) in m / s     (0., 0., 0.)>

obstime = <Time object: scale='tt' format='jyear_str' value=J2000.000>