3C295

Get the data

  • Go online to the CADC web page

  • Select your target in Spatial Constraints -> Target (put 3C295), and then, select below using the following criteria:

    Optical -> CFHT -> MegaPrime -> All -> Calibrated -> Image -> Object

  • Click on the Search buttn. Make sure all exposure have an integration time of at least 200s (Int Time -> >200), and the calibration is 2 (Cal. Lev). Mark them all using the button at the top of the list, and click on Download.

  • Click on URLS list in a file, download the list

  • Go to your terminal, and launch wget --content-disposition -i FILE_NAME (see the webpage for details) in the directory you want to get the file you just downloaded.

    cd WORKDIR/3C295
mkdir 00-CalibratedData
cd 00-CalibratedData
# the downloaded cadcUrlList.txt must be in the current directory
wget --content-disposition -i cadcUrlList.txt

  • Depending on your connection, this could take a little wile (300-400MB / file, ~100 files)

Re-organize the data

We first need to re-organize the data to get a directory with a structure compatible with the LSST stack.

cd WORKDIR/3C295
mkdir input
# Declare an instrument mapper for the DM butler
echo 'lsst.obs.cfht.MegacamMapper' > input/_mapper
setup pipe_tasks
setup obs_cfht # -t chotard depending on your install
ingestImages.py input CalibratedData/*.fz --mode link

The –mode link will create links instead of copying file

Get the astrometry

A script available at CC-IN2P3 will help you get the needed astrometry files using as input the list of calibrated data downloaded in the first step (cadcUrlList.txt). It is for now stored under

/sps/lsst/dev/nchotard/scripts/get_astrometry.py

but will soon be uploaded on github. To run it, do:

cd WORKDIR/3c295
mkdir 01-AstrometryData
cd AstrometryData
get_astrometry WORKDIR/3C295/00-CalibratedData/cadcUrlList.txt

Here is in some details what the script does.

The coordinate of the cluster are (RA, DEC) = (212.8355, 52.20277) in degree. They also come from CADC. At the moment the most complete catalog available is based on SDSS DR9 and is available at IN2P3 in:

/sps/lsst/data/astrometry_net_data/sdss-dr9 (1440 files)

To get the specific files that you need for the cluster analysis, you will use

get-healpix -N8 212.8355 -- 52.20277  # "--" is optional in this case but mandatory for a negative declination value

Which will return

(RA, DEC) = (212.835, 52.2028) degrees
Healpix=157 in the XY scheme (bighp=2, x=3, y=5)
  healpix=100 in the RING scheme (ringnum=7, longind=16)
  healpix=167 in the NESTED scheme.
Healpix center is (212.14286, 48.141208) degrees
Healpix is bounded by RA=[205.714, 218.571], Dec=[41.8103, 54.3409] degrees.
Healpix scale is 26384.5 arcsec.

This output give you the file number that you need to get (Healpix=157). Since each

Create the list of visit for each filters

To do so, use the build_visit_lists.py this way

build_visit_lists.py -i ../input

which should output something like

INFO: 96 visists found
INFO: 5 filters found
 - i: 20 visits -> i.list
 - r: 21 visits -> r.list
 - u: 25 visits -> u.list
 - z: 13 visits -> z.list
 - g: 17 visits -> g.list

Run processCcd for all filter

run_processCdd.py -F g -m -a