import astropy
astropy.__version__
'3.0.4'
import numpy as np
import astropy.units as u
import astropy.coordinates as coord
print(coord.ICRS.__doc__)
A coordinate or frame in the ICRS system.
If you're looking for "J2000" coordinates, and aren't sure if you want to
use this or `~astropy.coordinates.FK5`, you probably want to use ICRS. It's
more well-defined as a catalog coordinate and is an inertial system, and is
very close (within tens of milliarcseconds) to J2000 equatorial.
For more background on the ICRS and related coordinate transformations, see the
references provided in the :ref:`astropy-coordinates-seealso` section of the
documentation.
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 : `~astropy.units.Quantity`, optional, must be keyword
The Distance for this object along the line-of-sight.
(``representation`` must be None).
pm_ra_cosdec : :class:`~astropy.units.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 : :class:`~astropy.units.Quantity`, optional, must be keyword
The proper motion in Declination for this object (``pm_ra_cosdec`` must
also be given).
radial_velocity : :class:`~astropy.units.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.
# ICRS cartesian initialization works as in docstring
c = coord.ICRS(1,2,3, representation_type='cartesian')
c = coord.ICRS(x=1,y=2,z=3, representation_type='cartesian')
# Issue: But it looks like velocities cannot be unitless and need to be at least [1 /time]
# however the error message is confusing...
c = coord.ICRS(x=1,y=2,z=3, v_x=1, v_y=2, v_z=3, representation_type='cartesian', differential_type='cartesian')
---------------------------------------------------------------------------
ValueError Traceback (most recent call last)
<ipython-input-5-367a4f8fe60e> in <module>
1 # Issue: But it looks like velocities cannot be unitless and need to be at least [1 /time]
2 # however the error message is confusing...
----> 3 c = coord.ICRS(x=1,y=2,z=3, v_x=1, v_y=2, v_z=3, representation_type='cartesian', differential_type='cartesian')
~/miniconda3/envs/research/lib/python3.7/site-packages/astropy/coordinates/baseframe.py in __init__(self, copy, representation_type, differential_type, *args, **kwargs)
557 if differential_data:
558 self._data = representation_data.with_differentials(
--> 559 {'s': differential_data})
560 else:
561 self._data = representation_data # possibly None.
~/miniconda3/envs/research/lib/python3.7/site-packages/astropy/coordinates/representation.py in with_differentials(self, differentials)
732 copy=False)
733 new_rep._differentials.update(
--> 734 new_rep._validate_differentials(differentials))
735
736 return new_rep
~/miniconda3/envs/research/lib/python3.7/site-packages/astropy/coordinates/representation.py in _validate_differentials(self, differentials)
548 raise ValueError("For differential object '{0}', expected "
549 "unit key = '{1}' but received key = '{2}'"
--> 550 .format(repr(diff), expected_key, key))
551
552 # For now, we are very rigid: differentials must have the same shape
ValueError: For differential object '<CartesianDifferential (d_x, d_y, d_z) [dimensionless]
(1., 2., 3.)>', expected unit key = '' but received key = 's'
# The same docstring appears for coords.Galactic
# because the docstring templating gets it from `basefrome.py` `base_doc`.
# However, coords.Galactic cartesian coordinates are actually defined with names (u,v,w,U,V,W).
print(coord.Galactic.__doc__)
import inspect
print(inspect.getsource(coord.Galactic))
A coordinate or frame in the Galactic coordinate system.
This frame is used in a variety of Galactic contexts because it has as its
x-y plane the plane of the Milky Way. The positive x direction (i.e., the
l=0, b=0 direction) points to the center of the Milky Way and the z-axis
points toward the North Galactic Pole (following the IAU's 1958 definition
[1]_). However, unlike the `~astropy.coordinates.Galactocentric` frame, the
*origin* of this frame in 3D space is the solar system barycenter, not
the center of the Milky Way.
Parameters
----------
data : `BaseRepresentation` subclass instance
A representation object or ``None`` to have no data (or use the
coordinate component arguments, see below).
l : `Angle`, optional, must be keyword
The Galactic longitude for this object (``b`` must also be given and
``representation`` must be None).
b : `Angle`, optional, must be keyword
The Galactic latitude for this object (``l`` 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.
pm_l_cosb : :class:`~astropy.units.Quantity`, optional, must be keyword
The proper motion in Galactic longitude (including the ``cos(b)`` term)
for this object (``pm_b`` must also be given).
pm_b : :class:`~astropy.units.Quantity`, optional, must be keyword
The proper motion in Galactic latitude for this object (``pm_l_cosb``
must also be given).
radial_velocity : :class:`~astropy.units.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.
Notes
-----
.. [1] Blaauw, A.; Gum, C. S.; Pawsey, J. L.; Westerhout, G. (1960), "The
new I.A.U. system of galactic coordinates (1958 revision),"
`MNRAS, Vol 121, pp.123 <http://adsabs.harvard.edu/abs/1960MNRAS.121..123B>`_.
class Galactic(BaseCoordinateFrame):
"""
A coordinate or frame in the Galactic coordinate system.
This frame is used in a variety of Galactic contexts because it has as its
x-y plane the plane of the Milky Way. The positive x direction (i.e., the
l=0, b=0 direction) points to the center of the Milky Way and the z-axis
points toward the North Galactic Pole (following the IAU's 1958 definition
[1]_). However, unlike the `~astropy.coordinates.Galactocentric` frame, the
*origin* of this frame in 3D space is the solar system barycenter, not
the center of the Milky Way.
"""
frame_specific_representation_info = {
r.SphericalRepresentation: [
RepresentationMapping('lon', 'l'),
RepresentationMapping('lat', 'b')
],
r.CartesianRepresentation: [
RepresentationMapping('x', 'u'),
RepresentationMapping('y', 'v'),
RepresentationMapping('z', 'w')
],
r.CartesianDifferential: [
RepresentationMapping('d_x', 'U', u.km/u.s),
RepresentationMapping('d_y', 'V', u.km/u.s),
RepresentationMapping('d_z', 'W', u.km/u.s)
]
}
default_representation = r.SphericalRepresentation
default_differential = r.SphericalCosLatDifferential
# North galactic pole and zeropoint of l in FK4/FK5 coordinates. Needed for
# transformations to/from FK4/5
# These are from the IAU's definition of galactic coordinates
_ngp_B1950 = FK4NoETerms(ra=192.25*u.degree, dec=27.4*u.degree)
_lon0_B1950 = Angle(123, u.degree)
# These are *not* from Reid & Brunthaler 2004 - instead, they were
# derived by doing:
#
# >>> FK4NoETerms(ra=192.25*u.degree, dec=27.4*u.degree).transform_to(FK5)
#
# This gives better consistency with other codes than using the values
# from Reid & Brunthaler 2004 and the best self-consistency between FK5
# -> Galactic and FK5 -> FK4 -> Galactic. The lon0 angle was found by
# optimizing the self-consistency.
_ngp_J2000 = FK5(ra=192.8594812065348*u.degree, dec=27.12825118085622*u.degree)
_lon0_J2000 = Angle(122.9319185680026, u.degree)
# this is not an issue when representation_data are given as arguments
c = coord.Galactic(1,2,3, representation_type='cartesian')
# but raises error which can be cryptic given the docstring
# same problem for velocities
c = coord.Galactic(x=1,y=2,z=3, representation_type='cartesian')
---------------------------------------------------------------------------
TypeError Traceback (most recent call last)
<ipython-input-8-20c6f4ecd20b> in <module>
1 # but raises error which can be cryptic given the docstring
2 # same problem for velocities
----> 3 c = coord.Galactic(x=1,y=2,z=3, representation_type='cartesian')
~/miniconda3/envs/research/lib/python3.7/site-packages/astropy/coordinates/baseframe.py in __init__(self, copy, representation_type, differential_type, *args, **kwargs)
580 raise TypeError(
581 'Coordinate frame got unexpected keywords: {0}'.format(
--> 582 list(kwargs)))
583
584 # We do ``is None`` because self._data might evaluate to false for
TypeError: Coordinate frame got unexpected keywords: ['x', 'y', 'z']
# works with correct names
c = coord.Galactic(u=1,v=2,w=3, representation_type='cartesian')
c = coord.Galactic(u=1,v=2,w=3, U=1/u.yr, V=1/u.yr, W=1/u.yr, representation_type='cartesian', differential_type='cartesian')
