search

CARTAvis / carta

To CARTA users, this repo holds the CARTA release packages. Please use this repo to log bugs and feature requests. These will be triaged by the development team and prioritised as necessary in the development cycles.
19 stars 0 forks source link

Feature request: HEALPix support #102

Open tvern23 opened 2 years ago

tvern23 commented 2 years ago

Just wanted to say it would be great if CARTA could use healpix maps. I understand it currently doesn't and not in development at the moment but it would be very useful.

Jordatious commented 2 years ago

Thanks Tessa. Can you outline your use case to motivate this? Would it be for a particular telescope or survey?

tvern23 commented 2 years ago

Well for instance I tried to make a whole sky mosaic of all the NVSS tiles in healpix format, but even convolved down in resolution a bit the file size of the resulting healpix map was too large for DS9 to open. I had heard CARTA's specialty was large files but then realised it couldn't do healpix. For those interested in working with very wide area maps (eg upcoming surveys like RACS, EMU, POSSUM, potentially eROSITA maps and more) all at once (rather than HiPs which you can look at but is harder to actually do measurements and work with) this might be good.

veggiesaurus commented 2 years ago

Based on my understanding of how DS9 handles healpix files (and the documentation here), I think it's basically attempting to convert the healpix FITS file into a 2D image on the fly, rather than displaying it as a hierarchical image (like in Aladin).

We could explore doing something similar, but proper curvilinear tile support is unlikely. What is the total size of your image? I wonder if there are other options. CARTA supports its own hierarchical file format (HDF5 files in the IDIA schema, converted with the fits2idia utility), which would be another option, if you can produce a normal FITS image using other HEALPix tools first.