def test_to_fits_tab_time_cube(gwcs_cube_with_separable_time):
# gWCS:
w = gwcs_cube_with_separable_time
# FITS WCS -SIP (for celestial) and -TAB (for spectral):
hdr, bt = w.to_fits(projection=models.Sky2Pix_TAN(name='TAN'))
# create FITS WCS object:
hdus = [fits.PrimaryHDU(np.zeros(w.array_shape), hdr)]
hdus.extend(bt)
hdulist = fits.HDUList(hdus)
fits_wcs = astwcs.WCS(hdulist[0].header, hdulist)
assert np.allclose(hdulist[1].data['coordinates'].ravel(), np.arange(128))
# test points:
(xmin, xmax), (ymin, ymax), (zmin, zmax) = w.bounding_box
np.random.seed(1)
x = xmin + (xmax - xmin) * np.random.random(5)
y = ymin + (ymax - ymin) * np.random.random(5)
z = zmin + (zmax - zmin) * np.random.random(5)
world_crds = w(x, y, z)
# test forward transformation:
assert np.allclose(world_crds, fits_wcs.wcs_pix2world(x, y, z, 0))
# test round-tripping:
assert np.allclose((x, y, z), fits_wcs.wcs_world2pix(*world_crds, 0), rtol=1e-5, atol=1e-5)
def test_transforms_compound(tmpdir):
tree = {
'compound':
astmodels.Shift(1) & astmodels.Shift(2) | astmodels.Sky2Pix_TAN()
| astmodels.Rotation2D()
| astmodels.AffineTransformation2D([[2, 0], [0, 2]], [42, 32]) +
astmodels.Rotation2D(32)
}
helpers.assert_roundtrip_tree(tree, tmpdir)
def project_to_tangent_plane(ra, dec, ra_ref, dec_ref, scale=1.):
"""Convert ra/dec coordinates into pixel coordinates using a tangent plane projection.
Theprojection's reference point has to be specified.
Scale is a convenience parameter that defaults to 1.0, in which case the returned pixel
coordinates are also in degree. Scale can be set to a pixel scale to return detector coordinates
in pixels
Parameters
----------
ra : float
Right Ascension in decimal degrees
dec: float
declination in decimal degrees
ra_ref : float
Right Ascension of reference point in decimal degrees
dec_ref: float
declination of reference point in decimal degrees
scale : float
Multiplicative factor that is applied to the returned values. Default is 1.0
Returns
-------
x,y : float
pixel coordinates in decimal degrees if scale = 1.0
"""
# for zenithal projections, i.e. gnomonic, i.e. TAN:
if isinstance(ra_ref, u.Quantity):
lonpole = 180. * u.deg
else:
lonpole = 180.
# tangent plane projection from phi/theta to x,y
tan = astmodels.Sky2Pix_TAN()
# compute native coordinate rotation to obtain phi and theta
rot_for_tan = astrotations.RotateCelestial2Native(ra_ref, dec_ref, lonpole)
phi_theta = rot_for_tan(ra, dec)
# pixel coordinates, x and y are in degree-equivalent
x, y = tan(phi_theta[0], phi_theta[1])
x = x * scale
y = y * scale
return x, y
