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spectral matching with different conventions in the headers #1283
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off by one channel? |
By a lot. The two red lines in the screenshot should be at the same channel (the profiles are identical). |
the spectral matching is done by AST based on the headers. Is it possible that the backend is passing incorrect headers for the CASA image? edit, no wait. I just re-read the issue. It's just the channel matching that seems to be the issue |
The issue is in The solution is to also set the correct units between both images |
So I guess if the header is defined in wavelength we need to provide a correct unit too. |
Luckily we have a map for default units already thanks to @duidae |
When exporting an image to a FITS file in CASA, there is an option to set the spectral convention as velocity in the header. So in principle we should see the original image and the exported image are perfectly matched with each others. However, we see an offset in the matched channel index.
test image
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