def _parse_dimension(dim):
"""
Parses the radius and returns it in the format expected by UKIDSS.
Parameters
----------
dim : str, `~astropy.units.Quantity`
Returns
-------
dim_in_min : float
The value of the radius in arcminutes.
"""
if isinstance(dim,
u.Quantity) and dim.unit in u.deg.find_equivalent_units():
dim_in_min = dim.to(u.arcmin).value
# otherwise must be an Angle or be specified in hours...
else:
try:
new_dim = commons.parse_radius(dim).degree
dim_in_min = u.Quantity(value=new_dim,
unit=u.deg).to(u.arcmin).value
except (u.UnitsException, coord.errors.UnitsError, AttributeError):
raise u.UnitsException("Dimension not in proper units")
return dim_in_min
def invert(self, dispersion_values):
if not hasattr(dispersion_values, 'unit'):
raise u.UnitsException(
'Must give a dispersion value with a valid unit')
if misc.isiterable(dispersion_values) and not isinstance(
dispersion_values, basestring):
dispersion_values = np.array(dispersion_values)
return float((dispersion_values - self.dispersion0) /
self.dispersion_delta) + self.pixel_index
def _parse_dimension(dim):
if isinstance(dim,
u.Quantity) and dim.unit in u.deg.find_equivalent_units():
if dim.unit not in ['arcsec', 'arcmin', 'deg']:
dim = dim.to(u.degree)
# otherwise must be an Angle or be specified in hours...
else:
try:
new_dim = commons.parse_radius(dim)
dim = u.Quantity(new_dim.degree, u.Unit('degree'))
except (u.UnitsException, coord.errors.UnitsError, AttributeError):
raise u.UnitsException("Dimension not in proper units")
return dim
def from_header(cls,
header,
unit=None,
spectroscopic_axis_number=1,
**kwargs):
"""
Load a simple linear Spectral WCS from a FITS header.
Respects the following keywords:
* CDELT or CD: delta-dispersion
* CRVAL: reference position
* CRPIX: reference pixel
* CUNIT: dispersion units (parsed by astropy.units)
Parameters
----------
header : str
FITS Filename or FITS Header instance
unit : astropy.units.Unit
Specified units. Overrides CUNIT1 if specified.
.. todo:: Allow FITS files or just headers to be passed...
"""
if isinstance(header, basestring):
header = fits.getheader(header, **kwargs)
if unit is None:
try:
unit = u.Unit(header.get('CUNIT%i' %
spectroscopic_axis_number))
except u.UnitsException:
raise u.UnitsException(
"No units were specified and CUNIT did not contain unit information."
)
cdelt = header.get('CDELT%i' % spectroscopic_axis_number)
if cdelt is None:
cdelt = header.get(
'CD%i_%i' %
(spectroscopic_axis_number, spectroscopic_axis_number))
crpix = header['CRPIX%i' % spectroscopic_axis_number]
crval = header['CRVAL%i' % spectroscopic_axis_number]
return cls(crval, cdelt, crpix - 1, unit=unit)
def _parse_radius(radius):
"""
Parses the radius and returns it in the format expected by NED.
Parameters
----------
radius : str, `~astropy.units.Quantity`
Returns
-------
radius_in_min : float
The value of the radius in arcminutes.
"""
if isinstance(radius, u.Quantity) and radius.unit in u.deg.find_equivalent_units():
radius_in_min = radius.to(u.arcmin).value
# otherwise must be an Angle or be specified in hours...
else:
try:
radius_in_min = commons.radius_to_unit(radius,u.arcmin)
except (u.UnitsException, coord.errors.UnitsError, AttributeError):
raise u.UnitsException("Dimension not in proper units")
return radius_in_min