Loading skymaps for public HSC data


I would like to use the same tracts, patches, pixel space as the public HSC PDR2 releases for my own imaging (VISTA NIR). Can I load the corners described on the public page:


And convert them to a skymap.pickle file? Or is there a standard procedure for generating HSC PDR2 skymaps that I can copy? My end aim is to have VISTA imaging with a one to one mapping between HSC imaging and VISTA patches that can be directly overlaid in pixel space.

Will the command line task makeDiscreteSkyMap.py be the best way to do this?

Many thanks for any interest in this issue.


If you use the same numbers as in the obs_subaru/config/makeSkyMap.py and obs_subaru/config/hsc/makeSkyMap.py files, then you should end up with exactly the same skymap as HSC. You should be able to check using the corners you mention on the public page. Whether you use makeDiscreteSkyMap.py or makeSkyMap.py depends on how extensive an area you’re processing. TBH, I always just use makeSkyMap.py.


Great thanks, I wondered if that was the case. FYI my current plan is to get the basic pipeline running with the Butler gen2 and then while I’m running tests on that try to repeat it with gen3. We could have a talk after that about updating obs_necam to gen3. I think the key thing that needs to be done is to write an astro_metadata_translator module for the instrument.

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… Now when I try to make coadds if I don’t specify the tract/patch it runs on the whole sky. Is there a simple way to load the skymap and perform ra/dec to tract/patch and vice versa? I see the TractInfo function


but not the reverse.

Thanks again for all your help James!

… ah I see this functionality in BaseSkyMap



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