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DM-44404: add nanojanskyToInstFlux to PhotoCalib #737

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DM-44404: add nanojanskyToInstFlux to PhotoCalib #737

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cf729ba
Add nanojanskyToInstFlux to PhotoCalib
parejkoj Jun 10, 2024
deb3fad
Fix typos in variable names
parejkoj Jun 10, 2024
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17 changes: 17 additions & 0 deletions include/lsst/afw/image/PhotoCalib.h
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Original file line number Diff line number Diff line change
Expand Up @@ -389,6 +389,23 @@ class PhotoCalib final : public table::io::PersistableFacade<PhotoCalib>, public
/// @overload magnitudeToInstFlux(double, lsst::geom::Point<double, 2> const &) const;
double magnitudeToInstFlux(double magnitude) const;

/**
* Convert nanojansky to instFlux (ADU).
*
* If passed point, use the exact calculation at that point, otherwise, use the mean scaling factor.
*
* Useful for computing expected instrumental flux from reference catalog sources.
*
* @param[in] nanojansky The flux in nanojanksies to convert.
* @param[in] point The position that flux is to be converted at.
*
* @returns Source instFlux in ADU.
*/
double nanojanskyToInstFlux(double nanojansky, lsst::geom::Point<double, 2> const &point) const;

/// @overload nanojanskyToInstFlux(double, lsst::geom::Point<double, 2> const &) const;
double nanojanskyToInstFlux(double nanojansky) const;

/**
* Get the mean photometric calibration.
*
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13 changes: 11 additions & 2 deletions python/lsst/afw/image/_photoCalib.cc
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Expand Up @@ -154,10 +154,19 @@ void declarePhotoCalib(lsst::utils::python::WrapperCollection &wrappers) {
cls.def("magnitudeToInstFlux",
py::overload_cast<double, lsst::geom::Point<double, 2> const &>(
&PhotoCalib::magnitudeToInstFlux, py::const_),
"instFlux"_a, "point"_a);
"magnitude"_a, "point"_a);
cls.def("magnitudeToInstFlux",
py::overload_cast<double>(&PhotoCalib::magnitudeToInstFlux, py::const_),
"instFlux"_a);
"magnitude"_a);

/* from nanojansky. */
cls.def("nanojanskyToInstFlux",
py::overload_cast<double, lsst::geom::Point<double, 2> const &>(
&PhotoCalib::nanojanskyToInstFlux, py::const_),
"nanojansky"_a, "point"_a);
cls.def("nanojanskyToInstFlux",
py::overload_cast<double>(&PhotoCalib::nanojanskyToInstFlux, py::const_),
"nanojansky"_a);

/* utilities */
cls.def("getCalibrationMean", &PhotoCalib::getCalibrationMean);
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10 changes: 10 additions & 0 deletions src/image/PhotoCalib.cc
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Expand Up @@ -65,6 +65,8 @@ double toInstFluxFromMagnitude(double magnitude, double scale) {
return utils::ABMagnitudeToNanojansky(magnitude) / scale;
}

double toInstFluxFromNanojansky(double nanojansky, double scale) { return nanojansky / scale; }

double toNanojanskyErr(double instFlux, double instFluxErr, double scale, double scaleErr,
double nanojansky) {
return std::abs(nanojansky) * hypot(instFluxErr / instFlux, scaleErr / scale);
Expand Down Expand Up @@ -219,6 +221,14 @@ double PhotoCalib::magnitudeToInstFlux(double magnitude, lsst::geom::Point<doubl
return toInstFluxFromMagnitude(magnitude, evaluate(point));
}

double PhotoCalib::nanojanskyToInstFlux(double nanojansky) const {
return toInstFluxFromNanojansky(nanojansky, _calibrationMean);
}

double PhotoCalib::nanojanskyToInstFlux(double nanojansky, lsst::geom::Point<double, 2> const &point) const {
return toInstFluxFromNanojansky(nanojansky, evaluate(point));
}

std::shared_ptr<math::BoundedField> PhotoCalib::computeScaledCalibration() const {
return *(_calibration) / _calibrationMean;
}
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14 changes: 14 additions & 0 deletions tests/test_photoCalib.py
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Expand Up @@ -258,6 +258,20 @@ def _testPhotoCalibCenter(self, photoCalib, calibrationErr):
photoCalib.magnitudeToInstFlux(mag2, self.pointXShift),
rtol=1e-15)

# test reverse conversion: nanojansky to instFlux (no position specified)
self.assertFloatsAlmostEqual(self.instFlux1, photoCalib.nanojanskyToInstFlux(self.flux1))
self.assertFloatsAlmostEqual(self.instFlux2, photoCalib.nanojanskyToInstFlux(self.flux2), rtol=1e-15)

# test round-tripping instFlux->nanojansky->instFlux (position specified)
flux = photoCalib.instFluxToNanojansky(self.instFlux1, self.pointXShift)
self.assertFloatsAlmostEqual(self.instFlux1,
photoCalib.nanojanskyToInstFlux(flux, self.pointXShift),
rtol=1e-15)
flux2 = photoCalib.instFluxToNanojansky(self.instFlux2, self.pointXShift)
self.assertFloatsAlmostEqual(self.instFlux2,
photoCalib.nanojanskyToInstFlux(flux2, self.pointXShift),
rtol=1e-15)

# test round-tripping arrays (position specified)
instFlux1Array = np.full(10, self.instFlux1)
instFlux2Array = np.full(10, self.instFlux2)
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