Source code for pyEDITH.units
import astropy.units as u
import sys
import numpy as np
# Basic units
LENGTH = u.m
CM = u.cm
NM = u.nm
TIME = u.s
TEMPERATURE = u.K
ANGLE = u.rad
RADIAN = u.radian
WAVELENGTH = u.um
FREQUENCY = u.Hz
ENERGY = u.J
POWER = u.W
PHOTON_COUNT = u.photon
AREA = u.cm**2
JANSKY = u.Jy
# Astronomical units
DISTANCE = u.pc
AU = u.au
LUMINOSITY = u.L_sun
REARTH = u.R_earth
MAGNITUDE = u.mag
FLUX = u.W / u.m**2
FLUX_DENSITY = u.W / (u.m**2 * u.Hz)
# Angular units
ARCSEC = u.arcsec
MAS = u.mas
DEG = u.deg
INV_SQUARE_ARCSEC = u.def_unit("arcsec^-2", u.arcsec**-2)
# Time units
SECOND = u.s
MINUTE = u.min
HOUR = u.hour
DAY = u.day
YEAR = u.year
# Custom units
READ = u.def_unit("read", doc="Detector read")
FRAME = u.def_unit("frame", doc="Detector frame")
ZODI = u.def_unit(
"zodi", doc="Unit of zodiacal light intensity", represents=u.dimensionless_unscaled
)
# Spectral units
SPECTRAL_FLUX_DENSITY_CGS = u.erg / (u.cm**2 * u.s * u.Hz)
PHOTON_FLUX_DENSITY = PHOTON_COUNT / (u.cm**2 * u.s * u.nm)
PHOTON_FLUX_DENSITY_HZ = PHOTON_COUNT / (u.cm**2 * u.s * u.Hz)
SPECTRAL_FLUX_DENSITY_CGS_WAVELENGTH = u.erg / (u.s * u.cm**3)
PHOTON_FLUX_DENSITY_CGS_WAVELENGTH = PHOTON_COUNT / (u.s * u.cm**3)
PHOTON_SPECTRAL_RADIANCE = PHOTON_COUNT / (u.cm**2 * u.s * u.nm * u.arcsec**2)
PHOTON_SPECTRAL_RADIANCE_SR = u.photon / (u.cm**2 * u.nm * u.s * u.sr)
SURFACE_BRIGHTNESS = u.mag / u.arcsec**2
SPECTRAL_RADIANCE = u.W / (u.m**2 * u.sr * u.um)
SPECTRAL_RADIANCE_CGS = u.erg / (u.s * u.cm**2 * u.arcsec**2 * u.nm)
SPECTRAL_RADIANCE_CGS_AA = u.erg / (u.cm**2 * u.AA * u.s * u.sr)
# Dimensionless units
DIMENSIONLESS = u.dimensionless_unscaled
# Telescope-specific units
LAMBDA_D = u.def_unit(
"λ/D",
doc="Dimensionless unit of angular resolution in terms of wavelength over telescope diameter",
represents=u.dimensionless_unscaled,
)
PIXEL = u.pix
ELECTRON = u.electron
# Derived units
DARK_CURRENT = ELECTRON / (PIXEL * SECOND)
READ_NOISE = ELECTRON / (PIXEL * READ)
READ_TIME = SECOND / READ
CLOCK_INDUCED_CHARGE = ELECTRON / (PIXEL * FRAME) # from Chris 2019 paper
QUANTUM_EFFICIENCY = ELECTRON / PHOTON_COUNT
COUNT_RATE = ELECTRON / SECOND
# Equivalencies
EQUIV_ANGLE = u.equivalencies.dimensionless_angles()
[docs]
def lambda_d_to_radians(
value_lod: u.Quantity, wavelength: u.Quantity, diameter: u.Quantity
) -> u.Quantity:
"""
Convert a λ/D value to radians.
This function converts an angular measurement in units of λ/D (diffraction
limited resolution elements) to radians based on the provided wavelength
and telescope diameter.
Parameters
----------
value_lod : u.Quantity
The λ/D value (dimensionless)
wavelength : u.Quantity
The wavelength
diameter : u.Quantity
The telescope diameter
Returns
-------
u.Quantity
The angle in radians
"""
return (value_lod * wavelength / diameter).to(
ANGLE, equivalencies=u.dimensionless_angles()
)
[docs]
def radians_to_lambda_d(
angle: u.Quantity, wavelength: u.Quantity, diameter: u.Quantity
) -> u.Quantity:
"""
Convert an angle in radians to λ/D.
This function converts an angular measurement in radians to units of λ/D
(diffraction limited resolution elements) based on the provided wavelength
and telescope diameter.
Parameters
----------
angle : u.Quantity
The angle in radians
wavelength : u.Quantity
The wavelength
diameter : u.Quantity
The telescope diameter
Returns
-------
Quantity
The value in λ/D (dimensionless)
"""
return (angle * diameter / wavelength).to(
LAMBDA_D, equivalencies=u.dimensionless_angles()
)
[docs]
def lambda_d_to_arcsec(
value_lod: u.Quantity, wavelength: u.Quantity, diameter: u.Quantity
) -> u.Quantity:
"""
Convert λ/D to arcseconds.
This function converts an angular measurement in units of λ/D (diffraction
limited resolution elements) to arcseconds based on the provided wavelength
and telescope diameter.
Parameters
----------
value_lod : u.Quantity
The λ/D value (dimensionless)
wavelength : u.Quantity
Wavelength
diameter : u.Quantity
Telescope diameter
Returns
-------
u.Quantity
Angular size in arcseconds
"""
return lambda_d_to_radians(value_lod, wavelength, diameter).to(ARCSEC)
[docs]
def arcsec_to_lambda_d(
angle: u.Quantity, wavelength: u.Quantity, diameter: u.Quantity
) -> u.Quantity:
"""
Convert arcseconds to λ/D.
This function converts an angular measurement in arcseconds to units of λ/D
(diffraction limited resolution elements) based on the provided wavelength
and telescope diameter.
Parameters
----------
angle : u.Quantity
Angle in arcseconds
wavelength : u.Quantity
Wavelength
diameter : u.Quantity
Telescope diameter
Returns
-------
u.Quantity
Angular size in λ/D
"""
return radians_to_lambda_d(angle.to(ANGLE), wavelength, diameter)
[docs]
def arcsec_to_au(angle: u.Quantity, distance: u.Quantity) -> u.Quantity:
"""
Convert an angle in arcseconds to a distance in AU.
This function converts an angular separation in arcseconds to a projected
physical separation in astronomical units, given a distance to the system.
Parameters
----------
angle : u.Quantity
The angle in arcseconds
distance : u.Quantity
The distance in parsecs
Returns
-------
u.Quantity
The corresponding distance in AU
"""
return (angle.to_value(RADIAN) * distance).to(AU)
[docs]
def to_arcsec(quantity: u.Quantity, observer_distance: u.Quantity) -> float:
"""
Convert a physical size to an angular size in arcseconds.
This function converts a physical length to a projected angular size in
arcseconds as seen from a given distance. Important: quantity and
observer_distance must have the same units!
Parameters
----------
quantity : u.Quantity
The physical size to be converted to arcsec
observer_distance : u.Quantity
The distance to the object
Returns
-------
float
The corresponding angular size in arcsec
"""
return np.arctan(quantity / observer_distance).to_value(ARCSEC)
# Automatically generate ALL_UNITS list
ALL_UNITS = [
obj
for name, obj in sys.modules[__name__].__dict__.items()
if isinstance(obj, (u.UnitBase, u.CompositeUnit, u.IrreducibleUnit))
and name.isupper() # Only include uppercase variables (assuming they are constants)
]
