build_astrometric_error_model

lsst.validate.drp.astromerrmodel.build_astrometric_error_model(matchedMultiVisitDataset, selection, medianRef=100, matchRef=500)

Serializable model of astrometry errors across multiple visits.

\[\mathrm{astromRms} = C \theta / \mathrm{SNR} + \sigma_\mathrm{sys}\]

Parameters

matchedMultiVisitDatasetMatchedMultiVisitDataset

A dataset containing matched statistics for stars across multiple visits.

selectionnp.array of bool

The selection of sources to use to build the model.

medianReffloat or astropy.unit.Quantity, optional

Median reference astrometric scatter (default: milliarcsecond).

matchRefint, optional

Should match at least matchRef number of stars (dimensionless).

Returns

bloblsst.verify.Blob

Blob with datums:

• C: Model scaling factor.

• theta: Seeing (milliarcsecond).

• sigmaSys: Systematic error floor (milliarcsecond).

• astromRms: Astrometric scatter (RMS) for good stars (milliarcsecond).

Notes

The scatter and match defaults appropriate to SDSS are the defaults for medianRef and matchRef.

For SDSS, stars with mag < 19.5 should be completely well measured.