astro py:docs

- Index
- Modules

### Navigation

- Astropy v1.1.1 »
- Module code »

# Source code for astropy.coordinates.builtin_frames.cirs

    # -*- coding: utf-8 -*-
    # Licensed under a 3-clause BSD style license - see LICENSE.rst
    from __future__ import (absolute_import, unicode_literals, division,
                            print_function)

    from ..representation import SphericalRepresentation
    from ..baseframe import BaseCoordinateFrame, RepresentationMapping, TimeFrameAttribute
    from .utils import DEFAULT_OBSTIME

    class CIRS(BaseCoordinateFrame):
        """
        A coordinate or frame in the Celestial Intermediate Reference System (CIRS).

        This frame has one frame attribute:

        * ``obstime``
            The time at which the observation is taken.  Used for determining the
            position of the Earth and its precession.

        Parameters
        ----------
        representation : `BaseRepresentation` or None
            A representation object or None to have no data (or use the other keywords)
        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 : `~astropy.units.Quantity`, optional, must be keyword
            The Distance for this object along the line-of-sight.
            (``representation`` must be None).
        """

        frame_specific_representation_info = {
            'spherical': [RepresentationMapping('lon', 'ra'),
                          RepresentationMapping('lat', 'dec')]
        }
        frame_specific_representation_info['unitspherical'] = \
            frame_specific_representation_info['spherical']

        default_representation = SphericalRepresentation

        obstime = TimeFrameAttribute(default=DEFAULT_OBSTIME)

    #The "self-transform" is defined in icrs_cirs_transformations.py, because in
    #the current implementation it goes through ICRS (like GCRS)