HCRS

class astropy.coordinates.HCRS(*args, **kwargs)

Bases: astropy.coordinates.BaseRADecFrame

A coordinate or frame in a Heliocentric system, with axes aligned to ICRS.

The ICRS has an origin at the Barycenter and axes which are fixed with respect to space.

This coordinate system is distinct from ICRS mainly in that it is relative to the Sun’s center-of-mass rather than the solar system Barycenter. In principle, therefore, this frame should include the effects of aberration (unlike ICRS), but this is not done, since they are very small, of the order of 8 milli-arcseconds.

For more background on the ICRS and related coordinate transformations, see the references provided in the See Also section of the documentation.

The frame attributes are listed under Other Parameters.

Parameters:

representation : BaseRepresentation or None

A representation object or None to have no data (or use the other keywords 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.

copy : bool, optional

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

Other Parameters:  

obstime : Time

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

Attributes Summary

default_differential
default_representation
frame_attributes
frame_specific_representation_info
name
obstime

Attributes Documentation

default_differential

default_representation

frame_attributes = OrderedDict([('obstime', <astropy.coordinates.frame_attributes.TimeFrameAttribute object>)])

frame_specific_representation_info

name = 'hcrs'

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