AstrometryTask¶
AstrometryTask
matches a source catalog with objects from a reference
catalog and attempts to fit a WCS.
Processing summary¶
AstrometryTask
runs this sequence of operations:
Find position reference stars that overlap the exposure.
Match input source catalog to the position reference stars.
Fit a WCS based on the matches.
Python API summary¶
from lsst.meas.astrom.astrometry import AstrometryTask
-
class
AstrometryTask
(refObjLoader, schema=None, **kwargs) Match an input source catalog with objects from a reference catalog and solve for the WCS
...
- attributeconfig
Access configuration fields and retargetable subtasks.
See also
See the AstrometryTask
API reference for complete details.
Retargetable subtasks¶
matcher¶
- Default
lsst.meas.astrom.matchPessimisticB.MatchPessimisticBTask
- Field type
reference object/source matcher
referenceSelector¶
How to select reference objects for cross-matching.
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
How to select sources for cross-matching.
wcsFitter¶
- Default
lsst.meas.astrom.fitTanSipWcs.FitTanSipWcsTask
- Field type
WCS fitter
Configuration fields¶
doMagnitudeOutlierRejection¶
If True then a rough zeropoint will be computed from matched sources and outliers will be rejected in the iterations.
forceKnownWcs¶
If True then load reference objects and match sources but do not fit a WCS; this simply controls whether ‘run’ calls ‘solve’ or ‘loadAndMatch’
magnitudeOutlierRejectionNSigma¶
Number of sigma (measured from the distribution) in magnitude for a potential reference/source match to be rejected during iteration.
matchDistanceSigma¶
- Default
2
- Field type
- Range
[0,inf)
the maximum match distance is set to mean_match_distance + matchDistanceSigma*std_dev_match_distance; ignored if not fitting a WCS
maxIter¶
- Default
3
- Field type
- Range
[1,inf)
maximum number of iterations of match sources and fit WCSignored if not fitting a WCS
maxMeanDistanceArcsec¶
- Default
0.5
- Field type
- Range
[0,inf)
Maximum mean on-sky distance (in arcsec) between matched source and rerference objects post-fit. A mean distance greater than this threshold raises a TaskError and the WCS fit is considered a failure. The default is set to the maximum tolerated by the external global calibration (e.g. jointcal) step for conceivable recovery. Appropriate value will be dataset and workflow dependent.
minMatchDistanceArcSec¶
- Default
0.001
- Field type
- Range
[0,inf)
the match distance below which further iteration is pointless (arcsec); ignored if not fitting a WCS
sourceFluxType¶
Source flux type to use in source selection.
Examples¶
See lsst.pipe.tasks.photoCal.PhotoCalTask
.
Note
Task documentation is currently in the process of being converted from the old (Doxygen) system to this site. Until that conversion is complete, refer to the Doxygen documentation for PhotoCalTask.
Debugging¶
The lsst.pipe.base.cmdLineTask.CmdLineTask
command line task interface supports a flag -d to import debug.py from your PYTHONPATH; see lsstDebug
for more about debug.py files.
The available variables in AstrometryTask are
- display (bool)
If True display information at three stages: after finding reference objects, after matching sources to reference objects, and after fitting the WCS; defaults to False
- frame (int)
frame to use to display the reference objects; the next two frames are used to display the match list and the results of the final WCS; defaults to 0
To investigate the meas_astrom_astrometry_Debug, put something like
import lsstDebug
def DebugInfo(name):
debug = lsstDebug.getInfo(name) # N.b. lsstDebug.Info(name) would call us recursively
if name == "lsst.meas.astrom.astrometry":
debug.display = True
return debug
lsstDebug.Info = DebugInfo
into your debug.py file and run this task with the –debug flag.