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.

Methods Summary

`applySkyCorr`(calexp, skyCorr)	Apply sky correction to the input exposure.
`extractStamps`(inputExposure[, filterName, ...])	Identify the positions of bright stars within an input exposure using a reference catalog and extract them.
`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.
`warpStamps`(stamps, pixCenters)	Warps and shifts all given stamps so they are sampled on the same pixel grid and centered on the central pixel.

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.

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).

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.

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)