Source code for astropy.units.equivalencies
# Licensed under a 3-clause BSD style license - see LICENSE.rst
"""
A set of standard astronomical equivalencies.
"""
from __future__ import absolute_import, division, print_function, unicode_literals
from .._constants import si as _si
from . import si
from . import cgs
__all__ = ['spectral', 'spectral_density']
[docs]def spectral():
"""
Returns a list of equivalence pairs that handle spectral
wavelength, frequency, and energy equivalences.
Allows conversions between wavelength units, frequency units and
energy units as they relate to light.
"""
return [
(si.m, si.Hz, lambda x: _si.c / x),
(si.m, si.J, lambda x: (_si.c * _si.h) / x),
(si.Hz, si.J, lambda x: _si.h * x)
]
[docs]def spectral_density(sunit, sfactor):
"""
Returns a list of equivalence pairs that handle spectral density
with regard to wavelength and frequency.
"""
c_Aps = _si.c * 10 ** 10
flambda = cgs.erg / si.angstrom / si.cm ** 2 / si.s
fnu = cgs.erg / si.Hz / si.cm ** 2 / si.s
def converter(x):
return x * (sunit.to(si.AA, sfactor, spectral()) ** 2 / c_Aps)
def iconverter(x):
return x / (sunit.to(si.AA, sfactor, spectral()) ** 2 / c_Aps)
return [
(si.AA, fnu, converter, iconverter),
(flambda, fnu, converter, iconverter),
(si.AA, si.Hz, converter, iconverter),
(flambda, si.Hz, converter, iconverter)
]