build_astrometric_error_model

lsst.validate.drp.astromerrmodel.build_astrometric_error_model(matchedMultiVisitDataset, brightSnr=100, 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.

brightSnrfloat or astropy.unit.Quantity, optional

Minimum SNR for a star to be considered “bright” (dimensionless).

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:

• brightSnr: Threshold SNR for bright sources used in this model.

• 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.