How to Specify Skymap at NCSA RSP?

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#1

I’m trying to run Louise Edward’s tutorial, delegate-contributions-dp01/Structure/StructureAroundCluster/StructureAroundCluster_090521.ipynb, at NCSA and encountering skymap issues. It wants me to specify which skymap in this routine, and I’m not sure how to do that:
def cutout_coadd(butler, ra, dec, band=‘r’, datasetType=‘deepCoadd’,
cutoutSideLength=51, **kwargs):
“”"
Produce a cutout from a coadd at the given ra, dec position.

Adapted from DC2 tutorial notebook by Michael Wood-Vasey.

Parameters
----------
butler: lsst.daf.persistence.Butler
    Servant providing access to a data repository
ra: float
    Right ascension of the center of the cutout, in degrees
dec: float
    Declination of the center of the cutout, in degrees
band: string
    Filter of the image to load
datasetType: string ['deepCoadd']
    Which type of coadd to load.  Doesn't support 'calexp'
skymap: lsst.afw.skyMap.SkyMap [optional]
    Pass in to avoid the Butler read.  Useful if you have lots of them.
cutoutSideLength: float [optional]
    Size of the cutout region in pixels.

Returns
-------
MaskedImage
"""
radec = geom.SpherePoint(ra, dec, geom.degrees)
cutoutSize = geom.ExtentI(cutoutSideLength, cutoutSideLength)

if skymap is None:
    skymap = butler.get("skyMap")

# Look up the tract, patch for the RA, Dec
tractInfo = skymap.findTract(radec)
patchInfo = tractInfo.findPatch(radec)
xy = geom.PointI(tractInfo.getWcs().skyToPixel(radec))
bbox = geom.BoxI(xy - cutoutSize // 2, cutoutSize)
patch = tractInfo.getSequentialPatchIndex(patchInfo)

coaddId = {'tract': tractInfo.getId(), 'patch': patch, 'band': band}
parameters = {'bbox': bbox}

cutout_image = butler.get(datasetType, parameters=parameters,
                           dataId=coaddId)

return cutout_image

Select a position at roughly the center of the galaxy cluster:

cutout_image = cutout_coadd(butler, ra, dec, datasetType=‘deepCoadd’,
cutoutSideLength=501)
print("The size of the cutout in pixels is: ", cutout_image.image.array.shape)

This returns

UnboundLocalError Traceback (most recent call last)
/tmp/ipykernel_3588/2834475231.py in
1 # Select a position at roughly the center of the galaxy cluster:
----> 2 cutout_image = cutout_coadd(butler, ra, dec, datasetType=‘deepCoadd’,
3 cutoutSideLength=501)
4 print("The size of the cutout in pixels is: ", cutout_image.image.array.shape)

/tmp/ipykernel_3588/3823562161.py in cutout_coadd(butler, ra, dec, band, datasetType, cutoutSideLength, **kwargs)
31 cutoutSize = geom.ExtentI(cutoutSideLength, cutoutSideLength)
32
—> 33 if skymap is None:
34 skymap = butler.get(“skyMap”)
35

UnboundLocalError: local variable ‘skymap’ referenced before assignment

#2

I got it! I had to assign DC2 to skymap in dataID below, and I had to add it to the coaddId
radec = geom.SpherePoint(ra, dec, geom.degrees)
cutoutSize = geom.ExtentI(cutoutSideLength, cutoutSideLength)
if skymap is None:
dataID = {“skymap”: “DC2”}
skymap = butler.get(“skyMap”, dataID)
# Look up the tract, patch for the RA, Dec
tractInfo = skymap.findTract(radec)
patchInfo = tractInfo.findPatch(radec)
xy = geom.PointI(tractInfo.getWcs().skyToPixel(radec))
bbox = geom.BoxI(xy - cutoutSize // 2, cutoutSize)
patch = tractInfo.getSequentialPatchIndex(patchInfo)

coaddId = {'tract': tractInfo.getId(), 'patch': patch, 'band': band, "skymap": 'DC2'}
parameters = {'bbox': bbox}
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#3

I ran the notebook and could run it as-it-is without any issue. Your suggested solution seems to be making changes after the point from where the error was thrown. Can you check if the function signature was copied correctly?

#4

Thanks for helping out and attempting to recreate the issue @arunkannawadi !

This error and its solution only apply when running the notebook on the version of the Rubin Science Platform (RSP) deployed at NCSA, not at the Interim Data Facility (IDF; the Google Cloud, data.lsst.cloud) – the IDF is where all DP0 Delegates have their RSP accounts. So that is why you did not encounter the issue. Sorry for the confusion!

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