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SKA-INAF / scutout

Tool to extract source cutouts from a collection of FITS astronomical images
GNU General Public License v3.0
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BUNIT keyword lost after reprojection #7

Open cbordiu opened 4 years ago

cbordiu commented 4 years ago

Montage performs reprojection of multiple images on a common optimal header. For some reason, during this process, the BUNIT information is lost.

While this is not necessarily a problem if converting all the images to a common unit (Jy/beam), it becomes a critical issue if the conversion option is not set. We end up with images without information about the flux scale.

We need to study this carefully.

cbordiu commented 4 years ago

After some research, I think I've found the (possible) root of the problem. When using mImgtbl, one can specify via the parameter fieldlist, a list of header fields to be kept (apart from the default positional stuff). So it is possible to keep the BUNIT field, which is needed to perform flux conversions in mosaic mode.

Fieldlist has to be a text file describing the fields to be kept using the structure "NAME type size", e.g. "BUNIT char 15"

I think that we need to regenerate all the surveys metadata tables, and then, theoretically, we should be able to drag the BUNIT throughout all further montage operations.