ZogyImagePsfMatchTask

class lsst.ip.diffim.ZogyImagePsfMatchTask(*args, **kwargs)

Bases: lsst.ip.diffim.ImagePsfMatchTask

Task to perform Zogy PSF matching and image subtraction.

This class inherits from ImagePsfMatchTask to contain the _warper subtask and related methods.

Methods Summary

subtractExposures(templateExposure, …[, …])	Register, PSF-match, and subtract two Exposures using the ZOGY algorithm.
subtractMaskedImages(templateExposure, …)	!Psf-match and subtract two MaskedImages

Methods Documentation

subtractExposures(templateExposure, scienceExposure, doWarping=True, spatiallyVarying=True, inImageSpace=False, doPreConvolve=False)

Register, PSF-match, and subtract two Exposures using the ZOGY algorithm.

Do the following, in order: - Warp templateExposure to match scienceExposure, if their WCSs do not already match - Compute subtracted exposure ZOGY image subtraction algorithm on the two exposures

Parameters:

templateExposure : lsst.afw.image.Exposure

exposure to PSF-match to scienceExposure. The exposure’s mean value is subtracted in-place.

scienceExposure : lsst.afw.image.Exposure

reference Exposure. The exposure’s mean value is subtracted in-place.

doWarping : bool

what to do if templateExposure’s and scienceExposure’s WCSs do not match: - if True then warp templateExposure to match scienceExposure - if False then raise an Exception

spatiallyVarying : bool

If True, perform the operation over a grid of patches across the two exposures

inImageSpace : bool

If True, perform the Zogy convolutions in image space rather than in frequency space.

doPreConvolve : bool

*Currently not implemented.* If True assume we are to compute the match filter-convolved exposure which can be thresholded for detection. In the case of Zogy this would mean we compute the Scorr image.

Returns:

A `lsst.pipe.base.Struct` containing these fields:

- subtractedExposure: subtracted Exposure

- warpedExposure: templateExposure after warping to match scienceExposure (if doWarping true)

subtractMaskedImages(templateExposure, scienceExposure, doWarping=True, spatiallyVarying=True, inImageSpace=False, doPreConvolve=False)

!Psf-match and subtract two MaskedImages

Do the following, in order: - PSF-match templateMaskedImage to scienceMaskedImage - Determine the differential background - Return the difference: scienceMaskedImage -

((warped templateMaskedImage convolved with psfMatchingKernel) + backgroundModel)

@param templateMaskedImage: MaskedImage to PSF-match to scienceMaskedImage @param scienceMaskedImage: reference MaskedImage @param templateFwhmPix: FWHM (in pixels) of the Psf in the template image (image to convolve) @param scienceFwhmPix: FWHM (in pixels) of the Psf in the science image @param candidateList: a list of footprints/maskedImages for kernel candidates;

if None then source detection is run.

• Currently supported: list of Footprints or measAlg.PsfCandidateF

@return a pipeBase.Struct containing these fields: - subtractedMaskedImage = scienceMaskedImage - (matchedImage + backgroundModel) - matchedImage: templateMaskedImage convolved with psfMatchingKernel - psfMatchingKernel: PSF matching kernel - backgroundModel: differential background model - kernelCellSet: SpatialCellSet used to determine PSF matching kernel