ScaleZeroPointTask

class lsst.pipe.tasks.scaleZeroPoint.ScaleZeroPointTask(*args, **kwargs)

Bases: Task

Compute scale factor to scale exposures to a desired photometric zero point.

This simple version assumes that the zero point is spatially invariant.

Methods Summary

computeImageScaler(exposure[, dataRef])	Compute image scaling object for a given exposure.
getPhotoCalib()	Get desired PhotoCalib.
run(exposure[, dataRef])	Scale the specified exposure to the desired photometric zeropoint.
scaleFromFluxMag0(fluxMag0)	Compute the scale for the specified fluxMag0.
scaleFromPhotoCalib(calib)	Compute the scale for the specified PhotoCalib.

Methods Documentation

computeImageScaler(exposure, dataRef=None)

Compute image scaling object for a given exposure.

Parameters

exposurelsst.afw.image.Exposure

Exposure for which scaling is desired.

dataRefUnknown, optional

Data reference for exposure. Not used, but in API so that users can switch between spatially variant and invariant tasks.

getPhotoCalib()

Get desired PhotoCalib.

Returns

calibrationlsst.afw.image.PhotoCalib

Calibration with fluxMag0 set appropriately for config.zeroPoint.

run(exposure, dataRef=None)

Scale the specified exposure to the desired photometric zeropoint.

Parameters

exposurelsst.afw.image.Exposure

Exposure to scale; masked image is scaled in place.

dataRefUnknown, optional

Data reference for exposure. Not used, but in API so that users can switch between spatially variant and invariant tasks.

Returns

resultStruct

Results as a struct with attributes:

imageScaler

The image scaling object used to scale exposure.

scaleFromFluxMag0(fluxMag0)

Compute the scale for the specified fluxMag0.

This is a wrapper around scaleFromPhotoCalib, which see for more information.

Parameters

fluxMag0float

Flux at magnitude zero.

Returns

resultlsst.pipe.base.Struct

Results as a struct with attributes:

scale

Scale, such that if pixelCalib describes the photometric zeropoint of a pixel then the following scales that pixel to the photometric zeropoint specified by config.zeroPoint:

scale = computeScale(pixelCalib) pixel *= scale

scaleFromPhotoCalib(calib)

Compute the scale for the specified PhotoCalib.

Parameter

caliblsst.afw.image.PhotoCalib

PhotoCalib object to compute the scale from.

Returns

resultlsst.pipe.base.Struct

Results as a struct with attributes:

scale

Scale, such that if pixelCalib describes the photometric zeropoint of a pixel then the following scales that pixel to the photometric zeropoint specified by config.zeroPoint:

scale = computeScale(pixelCalib) pixel *= scale

Notes

Returns a struct to leave room for scaleErr in a future implementation.