ProcessBrightStarsTask

class lsst.pipe.tasks.processBrightStars.ProcessBrightStarsTask(initInputs=None, *args, **kwargs)

Bases: PipelineTask

Extract bright star cutouts; normalize and warp to the same pixel grid.

This task is used to extract, process, and store small image cut-outs (or “postage stamps”) around bright stars. It relies on three methods, called in succession:

extractStamps

Find bright stars within the exposure using a reference catalog and extract a stamp centered on each.

warpStamps

Shift and warp each stamp to remove optical distortions and sample all stars on the same pixel grid.

measureAndNormalize

Compute the flux of an object in an annulus and normalize it. This is required to normalize each bright star stamp as their central pixels are likely saturated and/or contain ghosts, and cannot be used.

Attributes Summary

canMultiprocess

Methods Summary

applySkyCorr(calexp, skyCorr)	Apply sky correction to the input exposure.
emptyMetadata()	Empty (clear) the metadata for this Task and all sub-Tasks.
extractStamps(inputExposure[, filterName, ...])	Identify the positions of bright stars within an input exposure using a reference catalog and extract them.
getFullMetadata()	Get metadata for all tasks.
getFullName()	Get the task name as a hierarchical name including parent task names.
getName()	Get the name of the task.
getTaskDict()	Get a dictionary of all tasks as a shallow copy.
makeField(doc)	Make a lsst.pex.config.ConfigurableField for this task.
makeSubtask(name, **keyArgs)	Create a subtask as a new instance as the name attribute of this task.
run(inputExposure[, refObjLoader, dataId, ...])	Identify bright stars within an exposure using a reference catalog, extract stamps around each, then preprocess them.
runQuantum(butlerQC, inputRefs, outputRefs)	Do butler IO and transform to provide in memory objects for tasks run method.
setModelStamp()	Compute (model) stamp size depending on provided buffer value.
timer(name[, logLevel])	Context manager to log performance data for an arbitrary block of code.
warpStamps(stamps, pixCenters)	Warps and shifts all given stamps so they are sampled on the same pixel grid and centered on the central pixel.

Attributes Documentation

canMultiprocess: ClassVar[bool] = True

Methods Documentation

applySkyCorr(calexp, skyCorr)

Apply sky correction to the input exposure.

Sky corrections can be generated using the SkyCorrectionTask. As the sky model generated via that task extends over the full focal plane, this should produce a more optimal sky subtraction solution.

Parameters:

calexpExposure or MaskedImage

Calibrated exposure to correct.

skyCorrBackgroundList

Full focal plane sky correction from SkyCorrectionTask.

Notes

This method modifies the input calexp in-place.

emptyMetadata() → None

Empty (clear) the metadata for this Task and all sub-Tasks.

extractStamps(inputExposure, filterName='phot_g_mean', refObjLoader=None, inputBrightStarStamps=None)

Identify the positions of bright stars within an input exposure using a reference catalog and extract them.

Parameters:

inputExposureExposureF

The image to extract bright star stamps from.

filterNamestr, optional

Name of the camera filter to use for reference catalog filtering.

refObjLoaderReferenceObjectLoader, optional

Loader to find objects within a reference catalog.

inputBrightStarStamps:

BrightStarStamps, optional Provides information about the stars that have already been extracted from the inputExposure in other steps of the pipeline. For example, this is used in the SubtractBrightStarsTask to avoid extracting stars that already have been extracted when running ProcessBrightStarsTask to produce brightStarStamps.

Returns:

resultStruct

Results as a struct with attributes:

starStamps

Postage stamps (list).

pixCenters

Corresponding coords to each star’s center, in pixels (list).

gMags

Corresponding (Gaia) G magnitudes (list).

gaiaIds

Corresponding unique Gaia identifiers (np.ndarray).

getFullMetadata() → TaskMetadata

Get metadata for all tasks.

Returns:

metadataTaskMetadata

The keys are the full task name. Values are metadata for the top-level task and all subtasks, sub-subtasks, etc.

Notes

The returned metadata includes timing information (if @timer.timeMethod is used) and any metadata set by the task. The name of each item consists of the full task name with . replaced by :, followed by . and the name of the item, e.g.:

topLevelTaskName:subtaskName:subsubtaskName.itemName

using : in the full task name disambiguates the rare situation that a task has a subtask and a metadata item with the same name.

getFullName() → str

Get the task name as a hierarchical name including parent task names.

Returns:

fullNamestr

The full name consists of the name of the parent task and each subtask separated by periods. For example:

• The full name of top-level task “top” is simply “top”.

• The full name of subtask “sub” of top-level task “top” is “top.sub”.

• The full name of subtask “sub2” of subtask “sub” of top-level task “top” is “top.sub.sub2”.

getName() → str

Get the name of the task.

Returns:

taskNamestr

Name of the task.

See also

getFullName

getTaskDict() → dict[str, weakref.ReferenceType[lsst.pipe.base.task.Task]]

Get a dictionary of all tasks as a shallow copy.

Returns:

taskDictdict

Dictionary containing full task name: task object for the top-level task and all subtasks, sub-subtasks, etc.

classmethod makeField(doc: str) → ConfigurableField

Make a lsst.pex.config.ConfigurableField for this task.

Parameters:

docstr

Help text for the field.

Returns:

configurableFieldlsst.pex.config.ConfigurableField

A ConfigurableField for this task.

Examples

Provides a convenient way to specify this task is a subtask of another task.

Here is an example of use:

class OtherTaskConfig(lsst.pex.config.Config):
    aSubtask = ATaskClass.makeField("brief description of task")

makeSubtask(name: str, **keyArgs: Any) → None

Create a subtask as a new instance as the name attribute of this task.

Parameters:

namestr

Brief name of the subtask.

**keyArgs

Extra keyword arguments used to construct the task. The following arguments are automatically provided and cannot be overridden:

• config.

• parentTask.

Notes

The subtask must be defined by Task.config.name, an instance of ConfigurableField or RegistryField.

run(inputExposure, refObjLoader=None, dataId=None, skyCorr=None)

Identify bright stars within an exposure using a reference catalog, extract stamps around each, then preprocess them.

Bright star preprocessing steps are: shifting, warping and potentially rotating them to the same pixel grid; computing their annular flux, and; normalizing them.

Parameters:

inputExposureExposureF

The image from which bright star stamps should be extracted.

refObjLoaderReferenceObjectLoader, optional

Loader to find objects within a reference catalog.

dataIddict or DataCoordinate

The dataId of the exposure (including detector) that bright stars should be extracted from.

skyCorrBackgroundList, optional

Full focal plane sky correction obtained by SkyCorrectionTask.

Returns:

brightStarResultsStruct

Results as a struct with attributes:

brightStarStamps

(BrightStarStamps)

runQuantum(butlerQC, inputRefs, outputRefs)

Do butler IO and transform to provide in memory objects for tasks run method.

Parameters:

butlerQCQuantumContext

A butler which is specialized to operate in the context of a lsst.daf.butler.Quantum.

inputRefsInputQuantizedConnection

Datastructure whose attribute names are the names that identify connections defined in corresponding PipelineTaskConnections class. The values of these attributes are the lsst.daf.butler.DatasetRef objects associated with the defined input/prerequisite connections.

outputRefsOutputQuantizedConnection

Datastructure whose attribute names are the names that identify connections defined in corresponding PipelineTaskConnections class. The values of these attributes are the lsst.daf.butler.DatasetRef objects associated with the defined output connections.

setModelStamp()

Compute (model) stamp size depending on provided buffer value.

timer(name: str, logLevel: int = 10) → Iterator[None]

Context manager to log performance data for an arbitrary block of code.

Parameters:

namestr

Name of code being timed; data will be logged using item name: Start and End.

logLevel

A logging level constant.

See also

lsst.utils.timer.logInfo

Examples

Creating a timer context:

with self.timer("someCodeToTime"):
    pass  # code to time

warpStamps(stamps, pixCenters)

Warps and shifts all given stamps so they are sampled on the same pixel grid and centered on the central pixel. This includes rotating the stamp depending on detector orientation.

Parameters:

stampsSequence [ExposureF]

Image cutouts centered on a single object.

pixCentersSequence [Point2D]

Positions of each object’s center (from the refCat) in pixels.

Returns:

resultStruct

Results as a struct with attributes:

warpedStars

Stamps of warped stars.

(list [MaskedImage])

warpTransforms

The corresponding Transform from the initial star stamp to the common model grid.

(list [TransformPoint2ToPoint2])

xy0s

Coordinates of the bottom-left pixels of each stamp, before rotation.

(list [Point2I])

nb90Rots

The number of 90 degrees rotations required to compensate for detector orientation.

(int)