How do I get a zeropoint for a particular sensor from the Butler?

Support
,
#1

Does anyone know how I get a zeropoint for a particular sensor from the butler?

#2

This seems to work fine:

lsst.afw.image.Calib(butler.get("calexp_md", ...)).getFluxMag0()

In addition, @rhl has pointed out that extracting the zeropoint is often unnecessary, and

calib.getMagnitude(flux, fluxErr)

should be used instead.

1 Like
#3

I.e.

calib = lsst.afw.image.Calib(butler.get("calexp_md", ...))
calib.getFluxMag0()

Iā€™m not all that happy requiring users to ask the butler for the metadata then contructing the Calib by hand ā€“ that seems like an implementation detail. Will the nbutler allow

calib = butler.get("calib", ...)

?

#4

The Old Butler can do that; it just requires more code embedded in a poor place. The New Butler should make it easier to have plugins that can do this without dependency issues.