FK4

class astropy.coordinates.FK4(*args, copy=True, representation_type=None, differential_type=None, **kwargs)[source] [edit on github]

Bases: astropy.coordinates.BaseRADecFrame

A coordinate or frame in the FK4 system.

Note that this is a barycentric version of FK4 - that is, the origin for this frame is the Solar System Barycenter, not the Earth geocenter.

The frame attributes are listed under Other Parameters.

Parameters:
data : BaseRepresentation subclass instance

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

ra : Angle, optional, must be keyword

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

dec : Angle, optional, must be keyword

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

distance : Quantity, optional, must be keyword

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

pm_ra_cosdec : Quantity, optional, must be keyword

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

pm_dec : Quantity, optional, must be keyword

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

radial_velocity : Quantity, optional, must be keyword

The radial velocity of this object.

representation_type : BaseRepresentation 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.

differential_type : BaseDifferential 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.

copy : bool, optional

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

Other Parameters:
 
equinox : Time

The equinox of this frame.

obstime : Time

The time this frame was observed. If None, will be the same as equinox.

Attributes Summary

default_differential
default_representation
equinox
frame_attributes
frame_specific_representation_info
name
obstime

Attributes Documentation

default_differential
default_representation
equinox = <Time object: scale='tai' format='byear_str' value=B1950.000>
frame_attributes = {'equinox': <astropy.coordinates.attributes.TimeAttribute object at 0x7f7ffef8a828>, 'obstime': <astropy.coordinates.attributes.TimeAttribute object at 0x7f7ffef8a7b8>}
frame_specific_representation_info
name = 'fk4'
obstime = None