build_photometric_error_model¶
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lsst.validate.drp.photerrmodel.build_photometric_error_model(matchedMultiVisitDataset, brightSnr=100, medianRef=100, matchRef=500)¶ Returns a serializable analytic photometry error model for a single visit.
This model is originally presented in http://arxiv.org/abs/0805.2366v4 (Eq 4, 5):
\[\begin{split}\sigma_1^2 &= \sigma_\mathrm{sys}^2 + \sigma_\mathrm{rand}^2 \\ x &= 10^{0.4(m-m_5)} \\ \sigma_\mathrm{rand}^2 &= (0.04 - \gamma) x + \gamma x^2~[\mathrm{mag}^2]\end{split}\]- Parameters
- matchedMultiVisitDataset
lsst.valididate.drp.matchreduce.MatchedMultiVisitDataset A dataset containing matched statistics for stars across multiple visits.
- brightSnr
floatorastropy.unit.Quantity, optional Minimum SNR for a star to be considered “bright.”
- medianRef
floatorastropy.unit.Quantity, optional Median reference astrometric scatter (millimagnitudes by default).
- matchRef
intorastropy.unit.Quantity, optional Should match at least matchRef stars.
- matchedMultiVisitDataset
- Returns
- blob
lsst.verify.Blob Blob with datums:
brightSnr: Threshold in SNR for bright sources used in this model.sigmaSys: Systematic error floor.gamma: Proxy for sky brightness and read noise.m5: 5-sigma photometric depth (magnitudes).photRms: RMS photometric scatter for ‘good’ stars (millimagnitudes).
- blob
Notes
The scatter and match defaults are appropriate to SDSS are stored here. For SDSS, stars with mag < 19.5 should be completely well measured. This limit is a band-dependent statement most appropriate to r.