legacy imaging stamps of galaxies

[forero]

Write a notebook with examples on how to plot stamps of galaxies given a TARGETID.

Here is a recipe from @araichoor that should make it into a tutorial

I guess you can easily get the (ra, dec) from the lss catalog, provided the id.
then it s a simple bash command, e.g.:

wget -O tmp.jpeg "http://legacysurvey.org/viewer/jpeg-cutout/?layer=ls-dr9&ra=0.23790&dec=0.05840&pixscale=0.1&size=300"

and you can of course wrap that in python — and adjust the stamp properties, e.g.:

ra, dec = 0.2379, 0.0584
width_arcsec = 30
pixscale = 0.1
tmpfn = "tmp.jpeg"
size = int(width_arcsec / pixscale)
layer = "ls-dr9"
tmpstr = 'wget -O {} "http://legacysurvey.org/viewer/jpeg-cutout/?layer={}&ra={:.5f}&dec={:.5f}&pixscale={}&size={:.0f}"'.format(
    tmpfn, layer, ra, dec, pixscale, size
)
subprocess.check_call(tmpstr, stderr=subprocess.DEVNULL, shell=True)

[weaverba137]

Any reason not to use requests.get here instead of calling to an external process?

[araichoor]

no, no reason; I just copied some piece of code I had; any suggestion you d have is certainly better!

[moustakas]

In case it's helpful, here's my invocation using urllib.request.urlretrieve (assuming Anand's variables):

import socket
from urllib.request import urlretrieve

wait = 5 # wait 5 seconds
socket.setdefaulttimeout(wait)

url = 'https://www.legacysurvey.org/viewer/jpeg-cutout?ra=' + \
  f'{ra}&dec={dec}&width={size}&height={size}&layer={layer}'
try:
    urlretrieve(url, tmpfn)
except:
    print(f'No viewer cutout retrieved after {wait} seconds.')

[dstndstn]

Can I request that you use the URL https://www.legacysurvey.org/viewer/cutout.jpg (rather than jpeg-cutout)

[weaverba137]

I still think requests is the easiest way to go here, for example:

r = requests.get('https://www.legacysurvey.org/viewer/cutout.jpg', {'layer': 'ls-dr9', 'ra': 0.23790, 'dec': 0.05840, 'pixscale': 0.1, 'size': 300})

Though I'm not sure 'pixscale' is necessary.

[dstndstn]

pixscale probably defaults to 0.262"/pix if omitted - the native pixel scale of decam and the legacy surveys coadded images.