opticam.noise

Functions

`get_source_photons`(N_source, gain)	Get the number of source photons.
`get_sky_photons_per_pixel`(n_sky, gain)	Get the number of sky photons per pixel.
`get_dark_counts_per_pixel`(dark_curr, t_exp)	Get the number of dark counts per pixel.
`get_read_counts_per_pixel`(n_read)	Get the read noise per pixel.
`get_sky_stderr`(N_source, N_pix, n_sky, gain)	Get the standard error (in magnitudes) of the sky noise.
`get_shot_stderr`(N_source, gain)	Get the standard error (in magnitudes) of the shot noise.
`get_dark_stderr`(N_source, N_pix, n_dark, t_exp, gain)	Get the standard error (in magnitudes) of the dark current noise.
`get_read_stderr`(N_source, N_pix, n_read, gain)	Get the standard error (in magnitudes) of the readout noise.
`snr`(N_source, N_pix, N_bkg, n_sky, dark_curr, n_read, ...)	The (simplified) S/N ratio equation or CCD Equation (see Chapter 4.4 of Handbook of CCD Astronomy by Howell, 2006).
`snr_stderr`(N_source, N_pix, N_bkg, n_sky, dark_curr, ...)	The standard error (in magnitudes) on the CCD Equation (see Chapter 4.4 of Handbook of CCD Astronomy by Howell,
`get_noise_params`(file, catalog, background, psf_params)	Get the noise values of a science image.
`get_snrs`(file, background, catalog, psf_params)	Get the S/N ratios for the cataloged sources in a science image.
`characterise_noise`(file, background, catalog, psf_params)	Characterise the expected noise from an image and compare it to the measured noise for a number of cataloged

Module Contents

opticam.noise.get_source_photons(N_source, gain)

Get the number of source photons.

Parameters

N_sourceQuantity: The number of source counts [ADU].
gainQuantity: The gain [photons/ADU].

Returns

float: The number of source photons.

Parameters:

N_source (astropy.units.Quantity)
gain (astropy.units.Quantity)

Return type:

float

opticam.noise.get_sky_photons_per_pixel(n_sky, gain)

Get the number of sky photons per pixel.

Parameters

n_skyQuantity: The sky counts per unit pixel [ADU/pix].
gainQuantity: The gain [photons/ADU].

Returns

float: The number of sky photons per pixel.

Parameters:

n_sky (astropy.units.Quantity)
gain (astropy.units.Quantity)

Return type:

float

opticam.noise.get_dark_counts_per_pixel(dark_curr, t_exp)

Get the number of dark counts per pixel.

Parameters

dark_currQuantity: The dark current [ADU/pixel/second]
t_expQuantity: The exposure time [seconds].

Returns

float: The number of dark counts per pixel.

Parameters:

dark_curr (astropy.units.Quantity)
t_exp (astropy.units.Quantity)

Return type:

float

opticam.noise.get_read_counts_per_pixel(n_read)

Get the read noise per pixel.

Parameters

n_readQuantity: The number of counts due to read noise per pixel [ADU/pixel].

Returns

float: The read noise per pixel.

Parameters:: n_read (astropy.units.Quantity)
Return type:: float

opticam.noise.get_sky_stderr(N_source, N_pix, n_sky, gain)

Get the standard error (in magnitudes) of the sky noise.

Parameters

N_sourceQuantity: The total number of source counts.
N_pixint: The number of aperture pixels.
n_skyQuantity: The number of sky counts per pixel.
gain: Quantity: The detector gain.

Returns

float: The standard error (in magnitudes) of the sky noise.

Parameters:

N_source (astropy.units.Quantity)
N_pix (astropy.units.Quantity)
n_sky (astropy.units.Quantity)
gain (astropy.units.Quantity)

Return type:

float

opticam.noise.get_shot_stderr(N_source, gain)

Get the standard error (in magnitudes) of the shot noise.

Parameters

N_sourceQuantity: The total number of source counts.
gain: Quantity: The detector gain.

Returns

float: The standard error (in magnitudes) of the shot noise.

Parameters:

N_source (astropy.units.Quantity)
gain (astropy.units.Quantity)

Return type:

float

opticam.noise.get_dark_stderr(N_source, N_pix, n_dark, t_exp, gain)

Get the standard error (in magnitudes) of the dark current noise.

Parameters

N_sourceQuantity: The total number of source counts.
N_pixint: The number of aperture pixels.
dark_currQuantity: The number of dark current electrons per pixel per unit time.
t_exp: Quantity: The exposure time.
gain: Quantity: The detector gain.

Returns

float: The standard error (in magnitudes) of the dark current noise.

Parameters:

N_source (astropy.units.Quantity)
N_pix (astropy.units.Quantity)
n_dark (astropy.units.Quantity)
t_exp (astropy.units.Quantity)
gain (astropy.units.Quantity)

Return type:

float

opticam.noise.get_read_stderr(N_source, N_pix, n_read, gain)

Get the standard error (in magnitudes) of the readout noise.

Parameters

N_sourceQuantity: The total number of source counts.
N_pixint: The number of aperture pixels.
n_readQuantity: The number of electrons per pixel due to read noise.
gain: Quantity: The detector gain.

Returns

float: The standard error (in magnitudes) of the readout noise.

Parameters:

N_source (astropy.units.Quantity)
N_pix (astropy.units.Quantity)
n_read (astropy.units.Quantity)
gain (astropy.units.Quantity)

Return type:

float

opticam.noise.snr(N_source, N_pix, N_bkg, n_sky, dark_curr, n_read, t_exp, gain)

The (simplified) S/N ratio equation or CCD Equation (see Chapter 4.4 of Handbook of CCD Astronomy by Howell, 2006).

Parameters

N_sourceQuantity: The total number of source counts.
N_pixint: The number of aperture pixels.
N_bkgQuantity: The number of pixels used to estimate the background.
n_skyQuantity: The number of sky counts per pixel.
dark_currQuantity: The number of dark current electrons per pixel per unit time.
n_readQuantity: The number of electrons per pixel due to read noise.
t_exp: Quantity: The exposure time.
gain: Quantity: The detector gain.

Returns

float: The S/N ratio.

Parameters:

N_source (astropy.units.Quantity)
N_pix (astropy.units.Quantity)
N_bkg (astropy.units.Quantity)
n_sky (astropy.units.Quantity)
dark_curr (astropy.units.Quantity)
n_read (astropy.units.Quantity)
t_exp (astropy.units.Quantity)
gain (astropy.units.Quantity)

Return type:

float

opticam.noise.snr_stderr(N_source, N_pix, N_bkg, n_sky, dark_curr, n_read, t_exp, gain)

The standard error (in magnitudes) on the CCD Equation (see Chapter 4.4 of Handbook of CCD Astronomy by Howell, 2006).

Parameters

N_sourceQuantity: The total number of source counts.
N_pixint: The number of aperture pixels.
N_bkgQuantity: The number of pixels used to estimate the background.
n_skyQuantity: The number of sky counts per pixel.
dark_currQuantity: The number of dark current electrons per pixel per unit time.
n_readQuantity: The number of electrons per pixel due to read noise.
t_exp: Quantity: The exposure time.
gain: Quantity: The detector gain.

Returns

float: The standard error (in magnitudes) on the S/N ratio.

Parameters:

N_source (astropy.units.Quantity)
N_pix (astropy.units.Quantity)
N_bkg (astropy.units.Quantity)
n_sky (astropy.units.Quantity)
dark_curr (astropy.units.Quantity)
n_read (astropy.units.Quantity)
t_exp (astropy.units.Quantity)
gain (astropy.units.Quantity)

Return type:

float

opticam.noise.get_noise_params(file, catalog, background, psf_params)

Get the noise values of a science image.

Parameters

filestr: The path to the science image.
catalogQTable: The source catalog corresponding to the science image.
backgroundBaseBackground | Callable: The background estimator.
psf_paramsDict[str, float]: The PSF parameters.

Returns

Tuple[NDArray, NDArray, Quantity, Quantity, Quantity, Quantity, Quantity, Quantity]: The fluxes, flux errors, number of pixels, backgorund counts/pixel, dark current, readout noise, exposure time, and gain.

Parameters:

file (str)
catalog (astropy.table.QTable)
background (opticam.background.global_background.BaseBackground | Callable)
psf_params (Dict[str, float])

Return type:

Tuple[numpy.typing.NDArray, numpy.typing.NDArray, astropy.units.Quantity, astropy.units.Quantity, astropy.units.Quantity, astropy.units.Quantity, astropy.units.Quantity, astropy.units.Quantity, astropy.units.Quantity]

opticam.noise.get_snrs(file, background, catalog, psf_params)

Get the S/N ratios for the cataloged sources in a science image.

Parameters

filestr: The path to the science image.
backgroundBaseBackground | Callable: The background estimator.
catalogQTable: The source catalog corresponding to the science image.
psf_paramsDict[str, float]: The PSF parameters.

Returns

List[float]: The S/N for each source. Sources are ordered as they appear in catalog.

Parameters:

file (str)
background (opticam.background.global_background.BaseBackground | Callable)
catalog (astropy.table.QTable)
psf_params (Dict[str, float])

Return type:

List[float]

opticam.noise.characterise_noise(file, background, catalog, psf_params)

Characterise the expected noise from an image and compare it to the measured noise for a number of cataloged sources.

Parameters

filestr: The file path to the science image.
backgroundBaseBackground | Callable: The background estimator.
catalogQTable: The source catalog corresponding to the science image.
psf_paramsDict[str, float]: The PSF parameters.

Returns

Dict[str, NDArray]: The noies properties.

Parameters:

file (str)
background (opticam.background.global_background.BaseBackground | Callable)
catalog (astropy.table.QTable)
psf_params (Dict[str, float])

Return type:

Dict[str, numpy.typing.NDArray]