MeasurePsfTask¶

class lsst.pipe.tasks.measurePsf.MeasurePsfTask(schema=None, **kwargs)¶

Bases: lsst.pipe.base.Task

A task that selects stars from a catalog of sources and uses those to measure the PSF.

Parameters:	schema : `lsst.sfw.table.Schema` An `lsst.afw.table.Schema` used to create the output `lsst.afw.table.SourceCatalog`. **kwargs Keyword arguments passed to lsst.pipe.base.task.Task.__init__.

Notes

If schema is not None, ‘calib_psf_candidate’ and ‘calib_psf_used’ fields will be added to identify which stars were employed in the PSF estimation.

This task can add fields to the schema, so any code calling this task must ensure that these fields are indeed present in the input table.

The star selector is a subclass of lsst.meas.algorithms.starSelector.BaseStarSelectorTask “lsst.meas.algorithms.BaseStarSelectorTask” and the PSF determiner is a sublcass of lsst.meas.algorithms.psfDeterminer.BasePsfDeterminerTask “lsst.meas.algorithms.BasePsfDeterminerTask”

There is no establised set of configuration parameters for these algorithms, so once you start modifying parameters (as we do in @ref pipe_tasks_measurePsf_Example) your code is no longer portable.

Debugging:

display: If True, display debugging plots
displayExposure: display the Exposure + spatialCells
displayPsfCandidates: show mosaic of candidates
showBadCandidates: Include bad candidates
displayPsfMosaic: show mosaic of reconstructed PSF(xy)
displayResiduals: show residuals
normalizeResiduals: Normalise residuals by object amplitude

Additionally you can enable any debug outputs that your chosen star selector and psf determiner support.

Attributes Summary

usesMatches Return True if this task makes use of the “matches” argument to the run method

Methods Summary

`emptyMetadata`()	Empty (clear) the metadata for this Task and all sub-Tasks.
`getAllSchemaCatalogs`()	Get schema catalogs for all tasks in the hierarchy, combining the results into a single dict.
`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.
`getSchemaCatalogs`()	Get the schemas generated by this 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`(exposure, sources[, expId, matches])	Measure the PSF.
`timer`(name, logLevel)	Context manager to log performance data for an arbitrary block of code.

Attributes Documentation

usesMatches¶: Return True if this task makes use of the “matches” argument to the run method

Methods Documentation

emptyMetadata() → None¶: Empty (clear) the metadata for this Task and all sub-Tasks.

getAllSchemaCatalogs() → Dict[str, Any]¶

Get schema catalogs for all tasks in the hierarchy, combining the results into a single dict.

Returns:	schemacatalogs : `dict` Keys are butler dataset type, values are a empty catalog (an instance of the appropriate `lsst.afw.table` Catalog type) for all tasks in the hierarchy, from the top-level task down through all subtasks.

Notes

This method may be called on any task in the hierarchy; it will return the same answer, regardless.

The default implementation should always suffice. If your subtask uses schemas the override Task.getSchemaCatalogs, not this method.

getFullMetadata() → lsst.pipe.base._task_metadata.TaskMetadata¶

Get metadata for all tasks.

Returns:	metadata : `TaskMetadata` 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:	fullName : `str` 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:	taskName : `str` Name of the task.

See also

Task.getAllSchemaCatalogs

Notes

Warning

Subclasses that use schemas must override this method. The default implementation returns an empty dict.

This method may be called at any time after the Task is constructed, which means that all task schemas should be computed at construction time, not when data is actually processed. This reflects the philosophy that the schema should not depend on the data.

Returning catalogs rather than just schemas allows us to save e.g. slots for SourceCatalog as well.

getTaskDict() → Dict[str, weakref]¶

Get a dictionary of all tasks as a shallow copy.

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

classmethod makeField(doc: str) → lsst.pex.config.configurableField.ConfigurableField¶

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

Parameters:	doc : `str` Help text for the field.
Returns:	configurableField : `lsst.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) → None¶

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

Parameters:	name : `str` 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(exposure, sources, expId=0, matches=None)¶

Measure the PSF.

Parameters:

exposure : lsst.afw.image.Exposure: Exposure to process; measured PSF will be added.
sources : Unknown: Measured sources on exposure; flag fields will be set marking stars chosen by the star selector and the PSF determiner if a schema was passed to the task constructor.
expId : int, optional: Exposure id used for generating random seed.
matches : list, optional: A list of lsst.afw.table.ReferenceMatch objects (i.e. of lsst.afw.table.Match with @c first being of type lsst.afw.table.SimpleRecord and @c second type lsst.afw.table.SourceRecord — the reference object and detected object respectively) as returned by @em e.g. the AstrometryTask. Used by star selectors that choose to refer to an external catalog.

Returns:

measurement : lsst.pipe.base.Struct

PSF measurement as a struct with attributes:

psf: The measured PSF (also set in the input exposure).
cellSet: An lsst.afw.math.SpatialCellSet containing the PSF candidates as returned by the psf determiner.

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

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

Parameters:	name : `str` Name of code being timed; data will be logged using item name: `Start` and `End`. logLevel A `logging` level constant.

Navigation

MeasurePsfTask¶