SDSS - getting separate u, g, r, i, z frames from SWARP tool and astropy I am following this paper to extract the u,g,r,i,z image frames from the SDSS image fits files. I have the fits files downloaded (using the bulk data download option from SDSS) and tried to run the SWARP tool to get the resampled image as output, which I will access through astropy. I am still unclear on the exact parameters that will make up the entire SWARP command. So far I have:
swarp frame-i.fits[0] frame-r.fits[0] frame-g.fits[0] frame-u.fits[0] frame-z.fits[0] -SUBTRACT_BACK N -RESAMPLE Y -RESAMPLING_TYPE LANCZOS3 -IMAGE_SIZE 64,64 -IMAGEOUT_NAME attempt.fits

This is written with the description of it in the paper, which is:

With the command that has been run, I am getting quite noisy images as output that do not relay any sort of information. What am I doing wrong in this process?
What they did was the following: for each individual filter, they assembled overlapping frames into a combined, single-filter image. E.g., they combined several g-band images into a single g-band image, combined several r-band images into a single r-band image, etc. (So they ran SWarp five times, once for each filter.) They then put each combined single-filter image into a separate layer to create a five-layer &quot;datacube&quot;; this is their &quot;64x64x5 pixel datacube&quot;.
What you are telling SWarp to do is something different: combine five individual-filter images into a single &quot;$u+g+r+i+z$&quot; image. (People do sometimes do this sort of thing, though with SDSS images they would normally just use the g, r, and i images, since the u and z images are so low-S/N that they mainly just add noise to the result. And in any case this isn't what the paper you're interested in was doing.)