Thanks for reaching out.
Please note that the NOIRLab mass storage facility is currently down for maintenance. But once it's back up, you should be able to get a full image by using the 'access_url' field from a SIA query. For examples of using SIA to obtain the access_url, please see this example notebook:
https://github.com/astro-datalab/notebooks-latest/blob/master/04_HowTos/SiaService/How_to_use_the_Simple_Image_Access_service.ipynb
For NSC, you would specify the SIA service URL as:
DEF_ACCESS_URL = "https://datalab.noirlab.edu/sia/nsc_dr2"
svc = sia.SIAService(DEF_ACCESS_URL)
and then run your svc.search() query as shown in the notebook.
Once you found the row matching your image, extract the 'access_url' value, and strip from it the 'extn', 'POS', and 'SIZE' arguments. So, for example, turn an access_url like this one:
https://datalab.noirlab.edu/svc/cutout?col=&siaRef=c4d_150718_072640_osi_g_v1.fits.fz&extn=5&POS=335.0,0.0&SIZE=0.1,0.1
to this:
https://datalab.noirlab.edu/svc/cutout?col=&siaRef=c4d_150718_072640_osi_g_v1.fits.fz
(if you don't strip them, you will get a cutout, not the full FITS file).
You can then use at least any of these ways to download the full fits.fz file: wget, curl, your browser, or the download_file() function from astropy.utils.data
Finally, and maybe simplest: if you know the exact file name from somewhere else, you can simply construct a download URL like the one shown above.
Please let us know if you need more help. And thank you for your patience while the datacenter undergoes storage maintenance.
Best,
Robert