Details
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Type:
RFC
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Status: Implemented
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Resolution: Done
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Component/s: DM
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Labels:None
Description
Image differencing tests with DECam and HSC have identified problems with background subtraction using the default ip_diffim configs (DM-20555, DM-20484).
While investigation of these issues is ongoing, the performance improvements from adjusted configuration parameters are notable: ~15% reduction in false positives in DECam, and even larger in HSC. Accordingly we suggest changing the defaults.
If accepted, this RFC would change to the following default configurations in imageDifference.py:
config.differencer.subtract['al'].kernel.active.spatialBgOrder = 2
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config.differencer.doAddCalexpBackground = False
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The current defaults are 0 and True.
Yes please. While adding the calexp background back in should improve difference imaging results, in practice it doesn't right now. Changing these ip_diffim defaults to something that yields good results seems very sensible.