QuickFrameMeasurementTask¶

class lsst.pipe.tasks.quickFrameMeasurement.QuickFrameMeasurementTask(config, *, display=None, **kwargs)¶

Bases: lsst.pipe.base.Task

WARNING: An experimental new task with changable API! Do not rely on yet!

This task finds the centroid of the brightest source in a given CCD-image and returns its centroid and a rough estimate of the seeing/PSF.

It is designed for speed, such that it can be used in observing scripts to provide pointing offsets, allowing subsequent pointings to place a source at an exact pixel position.

The approach taken here is deliberately sub-optimal in the detection and measurement sense, with all optimisation being done for speed and robustness of the result.

A small set of unit tests exist for this task, which run automatically if afwdata is setup. These, however, are stricky unit tests, and will not catch algorithmic regressions. TODO: DM-29038 exists to merge a regression real test which runs against 1,000 LATISS images, but is therefore slow and requires access to the data.

Parameters:	config : `lsst.pipe.tasks.quickFrameMeasurement.QuickFrameMeasurementTaskConfig` Configuration class for the QuickFrameMeasurementTask. display : `lsst.afw.display.Display`, optional The display to use for showing the images, detections and centroids.
Returns:	result : `lsst.pipe.base.Struct` Return strucure containing whether the task was successful, the main source’s centroid, its the aperture fluxes, the ixx and iyy of the source, and the median ixx, iyy of the detections in the exposure. See run() method for further details.
Raises:	This task should never raise, as the run() method is enclosed in an except Exception block, so that it will never fail during observing. Failure modes should be limited to returning a return Struct() with the same structure as the success case, with all value set to np.nan but with result.success=False.

Methods Summary

`checkResult`(exp, centroid, srcNum, percentile)	Perform a final check that centroid location is actually bright.
`detectObjectsInExp`(exp, nSigma, nPixMin[, grow])	Run a very basic but fast threshold-based object detection on an exposure Return the footPrintSet for the objects in a postISR exposure.
`emptyMetadata`()	Empty (clear) the metadata for this Task and all sub-Tasks.
`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`(exp, *[, donutDiameter, doDisplay])	Calculate position, flux and shape of the brightest star in an image.
`timer`(name, logLevel)	Context manager to log performance data for an arbitrary block of code.

Methods Documentation

static checkResult(exp, centroid, srcNum, percentile)¶

Perform a final check that centroid location is actually bright.

Parameters:

exp : lsst.afw.image.Exposure: The exposure on which to operate
centroid : tuple of float: Location of the centroid in pixel coordinates
scrNum : int: Number of the source in the source catalog. Only used if the check is failed, for debug purposes.
percentile : float: Image’s percentile above which the pixel containing the centroid must be in order to pass the check.

Raises:

ValueError: Raised if the centroid’s pixel is not above the percentile threshold

static detectObjectsInExp(exp, nSigma, nPixMin, grow=0)¶

Run a very basic but fast threshold-based object detection on an exposure Return the footPrintSet for the objects in a postISR exposure.

Parameters:	exp : `lsst.afw.image.Exposure` Image in which to detect objects. nSigma : `float` nSigma above image’s stddev at which to set the detection threshold. nPixMin : `int` Minimum number of pixels for detection. grow : `int` Grow the detected footprint by this many pixels.
Returns:	footPrintSet : `lsst.afw.detection.FootprintSet` FootprintSet containing the detections.

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

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

getFullName

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

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(exp, *, donutDiameter=None, doDisplay=False)¶

Calculate position, flux and shape of the brightest star in an image.

Given an an assembled (and at least minimally ISRed exposure), quickly and robustly calculate the centroid of the brightest star in the image.

Parameters:

exp : lsst.afw.image.Exposure: The exposure in which to find and measure the brightest star.
donutDiameter : int or float, optional: The expected diameter of donuts in pixels for use in the centre of mass centroid measurement. If None is provided, the config option is used.
doDisplay : bool: Display the image and found sources. A diplay object must have been passed to the task constructor.

Returns:

result : lsst.pipe.base.Struct

Struct containing:: Whether the task ran successfully and found the object (bool) The object’s centroid (float, float) The object’s ixx, iyy (float, float) The object’s 70 pixel aperture flux (float) The object’s 25 pixel aperture flux (float) The images’s median ixx, iyy (float, float)

If unsuccessful, the success field is False and all other results are np.nan of the expected shape.

Notes

Because of this task’s involvement in observing scripts, the run method should never raise. Failure modes are noted by returning a Struct with the same structure as the success case, with all value set to np.nan and result.success=False.

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

QuickFrameMeasurementTask¶