Colorterm#

class lsst.pipe.tasks.colorterms.Colorterm(*args, **kw)#

Bases: Config

Colorterm correction for one pair of filters

Notes#

The transformed magnitude p’ is given by: p’ = primary + c0 + c1*(primary - secondary) + c2*(primary - secondary)**2

To construct a Colorterm, use keyword arguments: Colorterm(primary=primaryFilterName, secondary=secondaryFilterName, c0=c0value, c1=c1Coeff, c2=c2Coeff) where c0-c2 are optional. For example (omitting c2): Colorterm(primary=”g”, secondary=”r”, c0=-0.00816446, c1=-0.08366937)

This is subclass of Config. That is a bit of a hack to make it easy to store the data in an appropriate obs_* package as a config override file. In the long term some other means of persistence will be used, at which point the constructor can be simplified to not require keyword arguments. (Fixing DM-2831 will also allow making a custom constructor).

Attributes Summary

`c0`	Constant parameter (`float`, default `0.0`)
`c1`	First-order parameter (`float`, default `0.0`)
`c2`	Second-order parameter (`float`, default `0.0`)
`primary`	name of primary filter (`str`)
`secondary`	name of secondary filter (`str`)

Methods Summary

`getCorrectedMagnitudes`(refCat[, filterName])	Return the colorterm corrected magnitudes for a given filter.
`propagateFluxErrors`(primaryFluxErr, ...)
`transformMags`(primary, secondary)	Transform brightness
`transformSource`(source)	Transform the brightness of a source

Attributes Documentation

c0#: Constant parameter (float, default 0.0)

c1#: First-order parameter (float, default 0.0)

c2#: Second-order parameter (float, default 0.0)

primary#: name of primary filter (str)

secondary#: name of secondary filter (str)

Methods Documentation

getCorrectedMagnitudes(refCat, filterName='deprecatedArgument')#

Return the colorterm corrected magnitudes for a given filter.

Parameters#

refCatlsst.afw.table.SimpleCatalog: The reference catalog to apply color corrections to.
filterNamestr, deprecated: The camera filter to correct the reference catalog into. The filterName argument is unused and will be removed in v23.

Returns#

refMagnp.ndarray: The corrected AB magnitudes.
refMagErrnp.ndarray: The corrected AB magnitude errors.

Raises#

KeyError: Raised if the reference catalog does not have a flux uncertainty for that filter.

Notes#

WARNING: I do not know that we can trust the propagation of magnitude errors returned by this method. They need more thorough tests.

propagateFluxErrors(primaryFluxErr, secondaryFluxErr)#

transformMags(primary, secondary)#

Transform brightness

Parameters#

primaryfloat: Brightness in primary filter (magnitude).
secondaryfloat: Brightness in secondary filter (magnitude).

Returns#

transformedfloat: The transformed brightness (as a magnitude).

transformSource(source)#

Transform the brightness of a source

Parameters#

sourceUnknown: Source whose brightness is to be converted; must support get(filterName) (e.g. source.get(“r”)) method, as do afw::table::Source and dicts.

Returns#

transformedfloat: The transformed source magnitude.