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, image_err, source_coords, image_coords, psf_params)

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

Parameters

imageNDArray

The image. If local_background_estimator is undefined, this image will be background subtracted.

image_errNDArray

The error in the image.

source_coordsNDArray

The source coordinates in the catalogue.

image_coordsNone | NDArray

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)

• image_err (numpy.typing.NDArray)

• source_coords (numpy.typing.NDArray)

• image_coords (None | numpy.typing.NDArray)

• 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, image_err, 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.

image_errNDArray

The error in the image.

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)

• image_err (numpy.typing.NDArray)

• position (numpy.typing.NDArray)

• psf_params (Dict[str, float])

Return type:

Dict[str, List]

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, image_err, source_coords, image_coords, psf_params)

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

Parameters

imageNDArray

The image. If local_background_estimator is undefined, this image will be background subtracted.

image_errNDArray

The error in the image.

source_coordsNDArray

The source coordinates in the catalogue.

image_coordsNone | NDArray

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)

• image_err (numpy.typing.NDArray)

• source_coords (numpy.typing.NDArray)

• image_coords (None | numpy.typing.NDArray)

• psf_params (Dict[str, float])

Return type:

Dict[str, List]

compute_aperture_flux(data, error, position, psf_params)

Compute the aperture flux of a source in the image.

Parameters

dataNDArray

The image.

errorNDArray

The error in the image.

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] | 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:

• data (numpy.typing.NDArray)

• error (numpy.typing.NDArray)

• position (numpy.typing.NDArray)

• psf_params (Dict[str, float])

Return type:

Tuple[float, float] | Tuple[float, float, float, 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, image_err, source_coords, image_coords, psf_params)

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

Parameters

imageNDArray

The image. If local_background_estimator is undefined, this image will be background subtracted.

image_errNDArray

The error in the image.

source_coordsNDArray

The source coordinates in the catalogue.

image_coordsNone | NDArray

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)

• image_err (numpy.typing.NDArray)

• source_coords (numpy.typing.NDArray)

• image_coords (None | numpy.typing.NDArray)

• psf_params (Dict[str, float])

Return type:

Dict[str, List]

compute_optimal_flux(image, error, 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.

errorNDArray

The error in the image.

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)

• error (numpy.typing.NDArray)

• position (numpy.typing.NDArray)

• psf_params (Dict[str, float])

Return type:

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