LoadReferenceObjectsTask

Implementations must subclass this class, override the loadSkyCircle method, and will typically override the value of ConfigClass with a task-specific config class.

LoadReferenceObjectsTask acts as an abstract base class for tasks that load objects from a reference catalog in a particluar region of sky.

Python API summary

from lsst.meas.algorithms.loadReferenceObjects import LoadReferenceObjectsTask
classLoadReferenceObjectsTask(butler=None, *args, **kwargs)

Abstract gen2 base class to load objects from reference catalogs...

attributeconfig

Access configuration fields and retargetable subtasks.

See also

See the LoadReferenceObjectsTask API reference for complete details.

Retargetable subtasks

No subtasks.

Configuration fields

anyFilterMapsToThis

Default
None
Field type
str Field (optional)
Always use this reference catalog filter, no matter whether or what filter name is supplied to the loader. Effectively a trivial filterMap: map all filter names to this filter. This can be set for purely-astrometric catalogs (e.g. Gaia DR2) where there is only one reasonable choice for every camera filter->refcat mapping, but not for refcats used for photometry, which need a filterMap and/or colorterms/transmission corrections.

filterMap

Default
{}
Field type
DictField
Key type
str
Value type
str
Mapping of camera filter name: reference catalog filter name; each reference filter must exist in the refcat. Note that this does not perform any bandpass corrections: it is just a lookup.

pixelMargin

Default
250
Field type
int RangeField
Range
[0,inf)
Padding to add to 4 all edges of the bounding box (pixels)

requireProperMotion

Default
False
Field type
bool Field
Require that the fields needed to correct proper motion (epoch, pm_ra and pm_dec) are present?

In Depth

Catalog Schema

  • coord: ICRS position of star on sky (an lsst.geom.SpherePoint)
  • centroid: position of star on an exposure, if relevant (an lsst.afw.Point2D)
  • hasCentroid: is centroid usable? (a Flag)
  • <referenceFilterName>_flux: brightness in the specified reference catalog filter (nJy)
    Note: you can use astropy.units to convert from AB Magnitude to nJy: u.Magnitude(value, u.ABmag).to_value(u.nJy)
  • <referenceFilterName>_fluxErr (optional): brightness standard deviation (nJy); omitted if no data is available; possibly nan if data is available for some objects but not others
  • camFlux: brightness in default camera filter (nJy); omitted if defaultFilter not specified
  • camFluxErr: brightness standard deviation for default camera filter; omitted if defaultFilter not specified or standard deviation not available that filter
  • <cameraFilterName>_camFlux: brightness in specified camera filter (nJy)
  • <cameraFilterName>_camFluxErr (optional): brightness standard deviation in specified camera filter (nJy); omitted if no data is available;
    possibly nan if data is available for some objects but not others
  • photometric (optional): is the object usable for photometric calibration? (a Flag)
  • resolved (optional): is the object spatially resolved? (a Flag)
  • variable (optional): does the object have variable brightness? (a Flag)
  • coord_raErr: uncertainty in coord along the direction of right ascension (radian, an Angle) = uncertainty in ra * cos(dec); nan if unknown
  • coord_decErr: uncertainty in coord along the direction of declination (radian, an Angle);
    nan if unknown
The following are optional; fields should only be present if the information is available for at least some objects.

Numeric values are nan if unknown:

  • epoch: date of observation as TAI MJD (day)
  • pm_ra: proper motion along the direction of right ascension (rad/year, an Angle) = dra/dt * cos(dec)
  • pm_dec: proper motion along the direction of declination (rad/year, and Angle)
  • pm_raErr: uncertainty in pm_ra (rad/year)
  • pm_decErr: uncertainty in pm_dec (rad/year)
  • pm_ra_dec_Cov: covariance between pm_ra and pm_dec (rad2/year2)
  • pm_flag: set if proper motion, error or covariance is bad
  • parallax: parallax (rad, an Angle)
  • parallaxErr: uncertainty in parallax (rad)
  • parallax_flag: set if parallax value or parallaxErr is bad
  • coord_ra_pm_ra_Cov: covariance between coord_ra and pm_ra (rad2/year)
  • coord_ra_pm_dec_Cov: covariance between coord_ra and pm_dec (rad2/year)
  • coord_ra_parallax_Cov: covariance between coord_ra and parallax (rad2/year)
  • coord_dec_pm_ra_Cov: covariance between coord_dec and pm_ra (rad2/year)
  • coord_dec_pm_dec_Cov: covariance between coord_dec and pm_dec (rad2/year)
  • coord_dec_parallax_Cov: covariance between coord_dec and parallax (rad2/year)
  • pm_ra_parallax_Cov: covariance between pm_ra and parallax (rad2/year)
  • pm_dec_parallax_Cov: covariance between pm_dec and parallax (rad2/year)