HCRS

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

Bases: astropy.coordinates.BaseCoordinateFrame

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 abberation (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.

This frame has these frame attributes:

• obstime

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

Parameters:

representation : BaseRepresentation or None

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

ra : Angle, optional, must be keyword

Right ascension for this object (dec must also be given and representation must be None).

dec : Angle, optional, must be keyword

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).

copy : bool, optional

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

Attributes Summary

default_representation
frame_attributes
frame_specific_representation_info
name
obstime

Attributes Documentation

default_representation

frame_attributes = OrderedDict([('obstime', <astropy.coordinates.baseframe.TimeFrameAttribute object at 0x7f2fca9ffcd0>)])

frame_specific_representation_info

name = 'hcrs'

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