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This is a feature request to add a flux-conserving (and equivalently count-conserving) reprojection method to / from HEALPIX.
For HEALPIX <-> HEALPIX it would be trivial, just multiply / divide by 4 to the power of difference in HEALPIX order. E.g. if one gets a huge HEALPIX file but doesn't need the high resolution, one could downsample. Not sure if this should be in reproject or in healpy. @lpsinger Maybe this exists in healpy and I missed it?
For HEALPIX <-> normal WCS projection image I don't know how to do it. I thought HEALPIX pixel boundaries are great circles and the 4-corner polygon "exact" method from Montage could be used as well, but this page http://healpix.jpl.nasa.gov/html/intronode4.htm explains that pixel boundaries are not great circles on the sphere.
The use case I have for this count- and flux-preserving reprojection would be to be able to go back and forth between HEALPIX and normal projections and be able to do correct photometry of sources e.g. on FERMI data. @lpsinger Easy or hard to implement? Worth the effort?
The text was updated successfully, but these errors were encountered:
This is a feature request to add a flux-conserving (and equivalently count-conserving) reprojection method to / from HEALPIX.
For HEALPIX <-> HEALPIX it would be trivial, just multiply / divide by 4 to the power of difference in HEALPIX order. E.g. if one gets a huge HEALPIX file but doesn't need the high resolution, one could downsample. Not sure if this should be in
reproject
or inhealpy
. @lpsinger Maybe this exists inhealpy
and I missed it?For HEALPIX <-> normal WCS projection image I don't know how to do it. I thought HEALPIX pixel boundaries are great circles and the 4-corner polygon "exact" method from Montage could be used as well, but this page http://healpix.jpl.nasa.gov/html/intronode4.htm explains that pixel boundaries are not great circles on the sphere.
The use case I have for this count- and flux-preserving reprojection would be to be able to go back and forth between HEALPIX and normal projections and be able to do correct photometry of sources e.g. on FERMI data. @lpsinger Easy or hard to implement? Worth the effort?
The text was updated successfully, but these errors were encountered: