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  1. Request For Comments
  2. RFC-356

Provide reference catalog fluxes in Maggies

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    • RFC
    • Status: Retired
    • Resolution: Done
    • DM

    Description

      In order to ease the comparison of fluxes between our source catalogs and reference catalogs, I propose that the catalog in a sky circle or pixel box instantiated from a reference object loader provide fluxes in the same units as our source catalog fluxes (Maggies, per RFC-322). Also, our reference catalog standards need to be clearly documented in some location outside the source code (pipelines.lsst.io?).

      The on-disk representation can be in whatever units are most appropriate for that particular catalog. If those units are not Maggies, LoadReferenceObjectTask will convert before the catalog is provided to the user.

      This is a change from current reference catalog practice, where LoadReferenceObjectTask's docstring says that all fluxes are in units of jansky:

          - *referenceFilterName*_flux: brightness in the specified reference catalog filter (Jy)
              Note: the function lsst.afw.image.abMagFromFlux will convert flux in Jy to AB Magnitude.
          - *referenceFilterName*_fluxSigma (optional): brightness standard deviation (Jy);
              omitted if no data is available; possibly nan if data is available for some objects but not others
          - camFlux: brightness in default camera filter (Jy); omitted if defaultFilter not specified
          - camFluxSigma: brightness standard deviation for default camera filter;
              omitted if defaultFilter not specified or standard deviation not available that filter
          - *cameraFilterName*_camFlux: brightness in specified camera filter (Jy)
          - *cameraFilterName*_camFluxSigma (optional): brightness standard deviation
              in specified camera filter (Jy); omitted if no data is available;
              possibly nan if data is available for some objects but not others
      

      I believe the only impact of this RFC is direct users of reference catalogs: single frame calibration and meas_mosaic (and jointcal, which is what provoked this RFC). As such, this could be implemented before RFC-322, but is probably best implemented simultaneously with it.

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            Parejkoj John Parejko created issue -
            Parejkoj John Parejko made changes -
            Field Original Value New Value
            Link This issue relates to DM-9195 [ DM-9195 ]
            Parejkoj John Parejko made changes -
            Link This issue relates to RFC-322 [ RFC-322 ]
            jsick Jonathan Sick made changes -
            Link This issue is triggering DM-11044 [ DM-11044 ]
            tjenness Tim Jenness made changes -
            Description In order to ease the comparison of fluxes between our source catalogs and reference catalogs, I propose that the catalog in a sky circle or pixel box instantiated from a reference object loader provide fluxes in the same units as our source catalog fluxes (Maggies, per RFC-322). Also, our reference catalog standards need to be clearly documented in some location outside the source code (pipelines.lsst.io?).

            The on-disk representation can be in whatever units are most appropriate for that particular catalog. If those units are not Maggies, {{LoadReferenceObjectTask}} will convert before the catalog is provided to the user.

            This is a change from current reference catalog practice, where {{LoadReferenceObjectTask}}'s docstring says that all fluxes are in units of Jansky:

            {code}
                - *referenceFilterName*_flux: brightness in the specified reference catalog filter (Jy)
                    Note: the function lsst.afw.image.abMagFromFlux will convert flux in Jy to AB Magnitude.
                - *referenceFilterName*_fluxSigma (optional): brightness standard deviation (Jy);
                    omitted if no data is available; possibly nan if data is available for some objects but not others
                - camFlux: brightness in default camera filter (Jy); omitted if defaultFilter not specified
                - camFluxSigma: brightness standard deviation for default camera filter;
                    omitted if defaultFilter not specified or standard deviation not available that filter
                - *cameraFilterName*_camFlux: brightness in specified camera filter (Jy)
                - *cameraFilterName*_camFluxSigma (optional): brightness standard deviation
                    in specified camera filter (Jy); omitted if no data is available;
                    possibly nan if data is available for some objects but not others
            {code}

            I believe the only impact of this RFC is direct users of reference catalogs: single frame calibration and meas_mosaic (and jointcal, which is what provoked this RFC). As such, this could be implemented before RFC-322, but is probably best implemented simultaneously with it.
            In order to ease the comparison of fluxes between our source catalogs and reference catalogs, I propose that the catalog in a sky circle or pixel box instantiated from a reference object loader provide fluxes in the same units as our source catalog fluxes (Maggies, per RFC-322). Also, our reference catalog standards need to be clearly documented in some location outside the source code (pipelines.lsst.io?).

            The on-disk representation can be in whatever units are most appropriate for that particular catalog. If those units are not Maggies, {{LoadReferenceObjectTask}} will convert before the catalog is provided to the user.

            This is a change from current reference catalog practice, where {{LoadReferenceObjectTask}}'s docstring says that all fluxes are in units of jansky:

            {code}
                - *referenceFilterName*_flux: brightness in the specified reference catalog filter (Jy)
                    Note: the function lsst.afw.image.abMagFromFlux will convert flux in Jy to AB Magnitude.
                - *referenceFilterName*_fluxSigma (optional): brightness standard deviation (Jy);
                    omitted if no data is available; possibly nan if data is available for some objects but not others
                - camFlux: brightness in default camera filter (Jy); omitted if defaultFilter not specified
                - camFluxSigma: brightness standard deviation for default camera filter;
                    omitted if defaultFilter not specified or standard deviation not available that filter
                - *cameraFilterName*_camFlux: brightness in specified camera filter (Jy)
                - *cameraFilterName*_camFluxSigma (optional): brightness standard deviation
                    in specified camera filter (Jy); omitted if no data is available;
                    possibly nan if data is available for some objects but not others
            {code}

            I believe the only impact of this RFC is direct users of reference catalogs: single frame calibration and meas_mosaic (and jointcal, which is what provoked this RFC). As such, this could be implemented before RFC-322, but is probably best implemented simultaneously with it.
            Parejkoj John Parejko made changes -
            Planned End 01/Jul/17 12:22 AM 02/Aug/17 12:22 AM
            tjenness Tim Jenness made changes -
            Planned End 02/Aug/17 12:22 AM 26/Aug/17 12:00 AM
            tjenness Tim Jenness made changes -
            Remote Link This issue links to "Page (Confluence)" [ 15304 ]
            womullan Wil O'Mullane made changes -
            Remote Link This issue links to "Page (Confluence)" [ 15317 ]
            tjenness Tim Jenness made changes -
            Remote Link This issue links to "Page (Confluence)" [ 15317 ]
            mjuric Mario Juric made changes -
            Labels dm-sst
            Parejkoj John Parejko made changes -
            Planned End 26/Aug/17 12:00 AM 30/Sep/17 12:00 AM
            Parejkoj John Parejko made changes -
            Planned End 30/Sep/17 12:00 AM 12/Oct/17 12:00 AM
            Parejkoj John Parejko made changes -
            Link This issue is triggering DM-12572 [ DM-12572 ]
            Parejkoj John Parejko made changes -
            Status Proposed [ 10805 ] Adopted [ 10806 ]
            gpdf Gregory Dubois-Felsmann made changes -
            Link This issue is triggering DM-12129 [ DM-12129 ]
            tjenness Tim Jenness made changes -
            Link This issue relates to RFC-549 [ RFC-549 ]
            Parejkoj John Parejko made changes -
            Resolution Rejected [ 10301 ] Done [ 10000 ]
            Status Adopted [ 10806 ] Retired [ 10705 ]
            lguy Leanne Guy made changes -
            Labels dm-sst DM-SST dm-sst
            lguy Leanne Guy made changes -
            Labels DM-SST dm-sst DM-SST

            People

              Parejkoj John Parejko
              Parejkoj John Parejko
              Colin Slater, Jim Bosch, John Parejko, Jonathan Sick, Paul Price, Simon Krughoff (Inactive), Tim Jenness, Zeljko Ivezic
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                Updated:
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                Planned End:

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