opticam.photometers

Classes

`BasePhotometer`	Base class for performing photometry on OPTICAM catalogues.
`AperturePhotometer`	A photometer for performing aperture photometry.
`OptimalPhotometer`	A photometer that implements the optimal photometry method described in Naylor 1998, MNRAS, 296, 339-346.

Functions

`perform_photometry`(file, photometer, source_coords, ...)	Perform photometry on a file.
`get_growth_curve`(image, x_centroid, y_centroid, r_max)	Compute the growth curve for a point in an image.

Module Contents

class opticam.photometers.BasePhotometer(forced=False, source_matching_tolerance=5.0, local_background_estimator=None)

Bases: abc.ABC

Base class for performing photometry on OPTICAM catalogues.

Parameters:

forced (bool)
source_matching_tolerance (float)
local_background_estimator (opticam.background.local_background.BaseLocalBackground | Callable | None)

forced = False

source_matching_tolerance = 5.0

local_background_estimator = None

abstractmethod compute(image, dark_flux, background_rms, source_coords, image_coords, psf_params)

Compute the fluxes of the catalogued sources from the given image.

Parameters

imageNDArray: The image. If self.local_background_estimator is undefined, this image will be background subtracted.
dark_fluxfloat: The dark current’s “flux” contribution.
background_rmsNDArray | None: The background RMS. May be None if self.local_background_estimator is defined.
source_coordsNDArray: The source coordinates in the catalogue.
image_coordsNDArray | None: The source coordinates in the image. If match_sources is True, this will be used to match sources in the image to sources in the catalogue.
psf_paramsDict[str, float]: The PSF parameters for the camera used to take the image. This parameter is defined in the catalogue and has the following keys: ‘semimajor_sigma’ (in pixels), ‘semiminor_sigma’ (in pixels), and ‘orientation’ (in degrees).

Returns

Dict[str, List]: The photometry results.

Parameters:

image (numpy.typing.NDArray)
dark_flux (float)
background_rms (numpy.typing.NDArray | None)
source_coords (numpy.typing.NDArray)
image_coords (numpy.typing.NDArray | None)
psf_params (Dict[str, float])

Return type:

Dict[str, List]

get_position(source_coords, image_coords, source_index, psf_params)

Get the position of a source in an image.

Parameters

source_coordsNDArray: The source coordinates in the catalogue.
image_coordsNDArray | None: The source coordinates in the image.
source_indexint: The source index.
psf_paramsDict[str, float]: The PSF parameters for the camera used to take the image. This parameter is defined in the catalogue and has the following keys: ‘semimajor_sigma’ (in pixels), ‘semiminor_sigma’ (in pixels), and ‘orientation’ (in degrees).

Returns

NDArray: The source coordinates.

Parameters:

source_coords (numpy.typing.NDArray)
image_coords (numpy.typing.NDArray | None)
source_index (int)
psf_params (Dict[str, float])

Return type:

numpy.typing.NDArray | None

get_closest_source(source_coords, image_coords, source_index, psf_params)

Given a source, find the closest source in the catalogue.

Parameters

source_coordsNDArray: The source coordinates in the catalogue.
image_coordsNDArray | None: The source coordinates in the image.
source_indexint: The source index.
psf_paramsDict[str, float]: The PSF parameters for the camera used to take the image. This parameter is defined in the catalogue and has the following keys: ‘semimajor_sigma’ (in pixels), ‘semiminor_sigma’ (in pixels), and ‘orientation’ (in degrees).

Returns

NDArray | None: The coordinates of the closest source.

Parameters:

source_coords (numpy.typing.NDArray)
image_coords (numpy.typing.NDArray | None)
source_index (int)
psf_params (Dict[str, float])

Return type:

numpy.typing.NDArray | None

define_results_dict()

Define a results dictionary for the photometer depending on whether local_background_estimator is defined.

Returns

Dict[str, List]: The results dictionary with keys ‘flux’, ‘flux_error’. If local_background_estimator is defined, the dictionary will also contain ‘background’ and ‘background_error’.

Return type:: Dict[str, List]

pad_results_dict(results)

Pad the results dictionary with None values for flux and flux error, and background and background error if `local_background_estimator’ is defined. This is used when a source cannot be matched or its position is invalid.

Parameters

resultsDict[str, List]: The results dictionary to pad.

Returns

Dict[str, List]: The padded results dictionary.

Parameters:: results (Dict[str, List])
Return type:: Dict[str, List]

populate_results_dict(results, phot_function, image, dark_flux, background_rms, position, psf_params)

Populate the results dictionary with the computed flux, flux error, and background (if applicable) using the provided photometry function.

Parameters

resultsDict[str, List]: The results dictionary to populate.
phot_functionCallable: The photometry function to use for computing the flux and flux error. This function should take the image, image error, position, and PSF parameters as arguments and return the flux and flux error, and optionally the background and background error if local_background_estimator is defined.
imageNDArray: The image.
dark_fluxfloat: The dark current’s “flux” contribution.
background_rmsNDArray | None: The background RMS. May be None if self.local_background_estimator is defined.
positionNDArray: The position of the source in the image.
psf_paramsDict[str, float]: The PSF parameters for the camera used to take the image. This parameter is defined in the catalogue and has the following keys: ‘semimajor_sigma’ (in pixels), ‘semiminor_sigma’ (in pixels), and ‘orientation’ (in degrees).

Returns

Dict[str, List]: The updated results dictionary with the computed flux, flux error, and background (if applicable).

Parameters:

results (Dict[str, List])
phot_function (Callable)
image (numpy.typing.NDArray)
dark_flux (float)
background_rms (numpy.typing.NDArray | None)
position (numpy.typing.NDArray)
psf_params (Dict[str, float])

Return type:

Dict[str, List]

get_label()

Get the label of the photometer for labelling output.

Returns

str: The label.

Return type:: str

class opticam.photometers.AperturePhotometer(semimajor_axis=None, semiminor_axis=None, orientation=None, forced=False, source_matching_tolerance=5.0, local_background_estimator=None)

Bases: BasePhotometer

A photometer for performing aperture photometry.

Parameters:

semimajor_axis (int | None)
semiminor_axis (int | None)
orientation (float | None)
forced (bool)
source_matching_tolerance (float)
local_background_estimator (None | opticam.background.local_background.BaseLocalBackground)

semimajor_axis = None

semiminor_axis = None

orientation = None

compute(image, dark_flux, background_rms, source_coords, image_coords, psf_params)

Compute the fluxes of the catalogued sources from the given image.

Parameters

imageNDArray: The image. If self.local_background_estimator is undefined, this image will be background subtracted.
dark_fluxfloat: The dark current’s “flux” contribution.
background_rmsNDArray | None: The background RMS. May be None if self.local_background_estimator is defined.
source_coordsNDArray: The source coordinates in the catalogue.
image_coordsNDArray | None: The source coordinates in the image. If match_sources is True, this will be used to match sources in the image to sources in the catalogue.
psf_paramsDict[str, float]: The PSF parameters for the camera used to take the image. This parameter is defined in the catalogue and has the following keys: ‘semimajor_sigma’ (in pixels), ‘semiminor_sigma’ (in pixels), and ‘orientation’ (in degrees).

Returns

Dict[str, List]: The photometry results.

Parameters:

image (numpy.typing.NDArray)
dark_flux (float)
background_rms (numpy.typing.NDArray | None)
source_coords (numpy.typing.NDArray)
image_coords (numpy.typing.NDArray | None)
psf_params (Dict[str, float])

Return type:

Dict[str, List]

compute_aperture_flux(image, dark_flux, background_rms, position, psf_params)

Compute the aperture flux of a source in the image.

Parameters

imageNDArray: The image.
dark_fluxfloat: The dark current’s “flux” contribution.
background_rmsNDArray | None: The background RMS. May be None if self.local_background_estimator is defined.
positionNDArray: The position of the source.
psf_paramsDict[str, float]: The PSF parameters for the camera used to take the image. This parameter is defined in the catalogue and has the following keys: ‘semimajor_sigma’ (in pixels), ‘semiminor_sigma’ (in pixels), and ‘orientation’ (in degrees).

Returns

Tuple[float, float, float] | Tuple[float, float, float, float, float]: The flux, flux error, and signal-to-noise ratio. If local_background_estimator is defined, the background and its error are also returned.

Parameters:

image (numpy.typing.NDArray)
dark_flux (float)
background_rms (numpy.typing.NDArray | None)
position (numpy.typing.NDArray)
psf_params (Dict[str, float])

Return type:

Tuple[float, float, float] | Tuple[float, float, float, float, float]

get_aperture(position, psf_params)

Parameters:

position (numpy.typing.NDArray)
psf_params (Dict[str, float])

Return type:

photutils.aperture.EllipticalAperture

get_aperture_area(psf_params)

Get the area of the aperture.

Parameters

psf_paramsDict[str, float],: The PSF parameters.

Returns

float: The area of the aperture.

Parameters:: psf_params (Dict[str, float])
Return type:: float

class opticam.photometers.OptimalPhotometer(forced=False, source_matching_tolerance=5.0, local_background_estimator=None)

Bases: BasePhotometer

A photometer that implements the optimal photometry method described in Naylor 1998, MNRAS, 296, 339-346.

Parameters:

forced (bool)
source_matching_tolerance (float)
local_background_estimator (opticam.background.local_background.BaseLocalBackground | Callable | None)

compute(image, dark_flux, background_rms, source_coords, image_coords, psf_params)

Compute the fluxes of the catalogued sources from the given image.

Parameters

imageNDArray: The image. If self.local_background_estimator is undefined, this image will be background subtracted.
dark_fluxfloat: The dark current’s “flux” contribution.
background_rmsNDArray | None: The background RMS. May be None if self.local_background_estimator is defined.
source_coordsNDArray: The source coordinates in the catalogue.
image_coordsNDArray | None: The source coordinates in the image. If match_sources is True, this will be used to match sources in the image to sources in the catalogue.
psf_paramsDict[str, float]: The PSF parameters for the camera used to take the image. This parameter is defined in the catalogue and has the following keys: ‘semimajor_sigma’ (in pixels), ‘semiminor_sigma’ (in pixels), and ‘orientation’ (in degrees).

Returns

Dict[str, List]: The photometry results.

Parameters:

image (numpy.typing.NDArray)
dark_flux (float)
background_rms (numpy.typing.NDArray | None)
source_coords (numpy.typing.NDArray)
image_coords (numpy.typing.NDArray | None)
psf_params (Dict[str, float])

Return type:

Dict[str, List]

compute_optimal_flux(image, dark_flux, background_rms, position, psf_params)

Compute the optimal flux of a source in the image as described in Naylor 1998, MNRAS, 296, 339-346.

Parameters

imageNDArray: The image.
dark_fluxfloat: The dark current’s “flux” contribution.
background_rmsNDArray | None: The background RMS. May be None if self.local_background_estimator is defined.
positionNDArray: The position of the source in the image, given as (y, x) coordinates.
psf_paramsDict[str, float]: The PSF parameters for the camera used to take the image. This parameter is defined in the catalogue and has the following keys: ‘semimajor_sigma’ (in pixels), ‘semiminor_sigma’ (in pixels), and ‘orientation’ (in degrees).

Returns

Tuple[float, float] | Tuple[float, float, float, float]: The flux and flux error. If local_background_estimator is defined, the background and its error are also returned.

Parameters:

image (numpy.typing.NDArray)
dark_flux (float)
background_rms (numpy.typing.NDArray | None)
position (numpy.typing.NDArray)
psf_params (Dict[str, float])

Return type:

Tuple[float, float] | Tuple[float, float, float, float]

static get_weights(var, position, psf_params)

Compute the optimal weight for each pixel in an image.

Parameters

varNDArray: The variance image.
positionNDArray: The position of the source.
psf_paramsDict[str, float]: The PSF parameters.

Returns

Tuple[NDArray, float]: The weights and the normalisation constant.

Parameters:

var (numpy.typing.NDArray)
position (numpy.typing.NDArray)
psf_params (Dict[str, float])

Return type:

Tuple[numpy.typing.NDArray, float]

opticam.photometers.perform_photometry(file, photometer, source_coords, gains, bmjds, barycenter, flat_corrector, rebin_factor, remove_cosmic_rays, background, threshold, finder, psf_params, fltr, logger)

Perform photometry on a file.

Parameters

filestr: The file path.
photometerBasePhotometer: The photometer to use.
source_coordsNDArray: The coordinates of the sources.
gainsDict[str, float]: The image gain.
bmjdsDict[str, float]: The image time stamps.
barycenterbool: Whether to apply a barycentric correction to the image time stamps.
flat_correctorFlatFieldCorrector | None: The flat field corrector.
rebin_factorint: The software pixel rebinning factor.
remove_cosmic_raysbool: Whether to remove cosmic rays from the image.
backgroundBaseBackground: The two-dimensional background estimator.
thresholdfloat: The scalar source detection threshold in units of background RMS.
finderDefaultFinder: The source finder.
psf_paramsDict[str, Dict[str, float]]: The PSF parameters.
fltrstr: The image filter.
loggerLogger: The logger.

Returns

Dict[str, List]: The photometry results.

Parameters:

file (str)
photometer (BasePhotometer)
source_coords (numpy.typing.NDArray)
gains (Dict[str, float])
bmjds (Dict[str, float])
barycenter (bool)
flat_corrector (opticam.correctors.flat_field_corrector.FlatFieldCorrector | None)
rebin_factor (int)
remove_cosmic_rays (bool)
background (opticam.background.global_background.BaseBackground)
threshold (float)
finder (opticam.finders.DefaultFinder)
psf_params (Dict[str, Dict[str, float]])
fltr (str)
logger (logging.Logger)

Return type:

Dict[str, List]

opticam.photometers.get_growth_curve(image, x_centroid, y_centroid, r_max)

Compute the growth curve for a point in an image.

Parameters

imageNDArray: The image.
x_centroidfloat: The x centroid of the point.
y_centroidfloat: The y centroid of the point.
r_maxint: The maximum radius in pixels.

Returns

Tuple[NDArray, NDArray]: _description_

Parameters:

image (numpy.typing.NDArray)
x_centroid (float)
y_centroid (float)
r_max (int)

Return type:

Tuple[numpy.typing.NDArray, numpy.typing.NDArray]