FgcmBuildStarsTask¶
FgcmBuildStarsTask finds all the single-visit sources in a repository (or a subset based on command-line parameters) and extracts all the potential photometric calibration stars for input into fgcm. This task additionally uses fgcm to match star observations into unique stars, and performs as much cleaning of the input catalog as possible. A tutorial on the steps of running fgcmcal are found in the cookbook.
The fgcmcal code runs on calexp source catalogs from visits constrained by the --id parameter on the command line. Best results are obtained when fgcmcal is run with full visits.
In Gen2, due to limitations of the Gen2 Butler, optimal performance is obtained by specifying a single “reference” ccd on the command line (e.g. ccd=13) and setting the config variable checkAllCcds = True (which is the default). The alternative is to specify all the desired CCDs and set checkAllCcds = False, e.g., ccd=0..8^10..103. However, this is slower than the first option, and the improvement in speed in the first option is greater the more visits are specified. If instead you want to process all the visits in a rerun selected by filter, field, or some other dataid field, then by using a reference ccd and setting checkAllCcds = True you can speed things up by a factor of approximately 100 relative to the alternative (naming CCDs specifically).
Be aware that if a visit does not have a calexp available with the given reference CCD then it will be skipped. If this is possibly an issue, multiple reference ccds can be specified on the command line, although performance will degrade the more are specified.
At the current time, fgcmcal does not support Gen3.
This is the second task in a typical fgcmcal processing chain. The first is FgcmMakeLutTask, the third is FgcmFitCycleTask, and the fourth is FgcmOutputProductsTask.
FgcmBuildStarsTask is available as a command-line task, fgcmBuildStars.py.
Processing summary¶
FgcmBuildStarsTask runs this sequence of operations:
- Finds unique visits and collates visit metadata, including exposure time, pointing, typical psf size, background level.
- Reads in all sources, selecting good stars according to the chosen source selector.
- Matches sources internally across bands to get a unique multi-band list of possible calibration stars.
- Matches possible calibration stars to a reference catalog.
- All results are stored in the output repo
fgcm-processdirectory.
fgcmBuildStars.py command-line interface¶
fgcmBuildStars.py REPOPATH [@file [@file2 ...]] [--output OUTPUTREPO | --rerun RERUN] [--id] [other options]
Key arguments:
REPOPATH- The input Butler repository’s URI or file path.
Key options:
--id:- The data IDs to process.
See also
See Command-line task argument reference for details and additional options.
Python API summary¶
from lsst.fgcmcal.fgcmBuildStars import FgcmBuildStarsTask
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class
FgcmBuildStarsTask Build stars for the FGCM global calibration
...
-
attribute
config Access configuration fields and retargetable subtasks.
-
method
runDataRef Cross-match and make star list for FGCM Input
...
See also
See the FgcmBuildStarsTask API reference for complete details.
Butler datasets¶
When run as the fgcmBuildStars.py command-line task, or directly through the runDataRef method, FgcmBuildStarsTask obtains datasets from the input Butler data repository and persists outputs to the output Butler data repository.
Note that configurations for FgcmBuildStarsTask, and its subtasks, affect what datasets are persisted and what their content is.
Input datasets¶
src- Full-depth source catalog (
lsst.afw.table) produced byProcessCcdTask calexp- Calibrated exposure produced by
ProcessCcdTask(for exposure metadata) fgcmLookupTable- FGCM look-up table produced by FgcmMakeLutTask
Output datasets¶
fgcmVisitCatalog- Catalog (
lsst.afw.table) of visit metadata fgcmStarObservations- Catalog of star observations
fgcmStarIds- Catalog of unique star ids, positions, and number of observations
fgcmStarIndices- Catalog of indices linking unique star ids to star observations
fgcmReferenceStars- Catalog of reference stars matched to unique star ids.
Retargetable subtasks¶
fgcmLoadReferenceCatalog¶
- Default
lsst.fgcmcal.fgcmLoadReferenceCatalog.FgcmLoadReferenceCatalogTask- Field type
ConfigurableField
sourceSelector¶
- Default
'science'- Field type
- Single-selection
RegistryField - Choices
'science'lsst.meas.algorithms.sourceSelector.ScienceSourceSelectorTask'references'lsst.meas.algorithms.sourceSelector.ReferenceSourceSelectorTask'objectSize'lsst.meas.algorithms.objectSizeStarSelector.ObjectSizeStarSelectorTask'flagged'lsst.meas.algorithms.flaggedSourceSelector.FlaggedSourceSelectorTask'astrometry'lsst.meas.algorithms.astrometrySourceSelector.AstrometrySourceSelectorTask'matcher'lsst.meas.algorithms.matcherSourceSelector.MatcherSourceSelectorTask'diaCatalog'lsst.ip.diffim.diaCatalogSourceSelector.DiaCatalogSourceSelectorTask