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ASTCAT access to 2Mass and USNO-B1

  • Friday, August 17 2007 @ 06:12 PM GMT
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Code Snippets The ASTCAT package provides tools to get catalogs from web sites that support HTTP/Get URLs which return a text table. It is challenge to discover these sites and keep the the ASTCAT database up-to-date. Two important catalogs are the 2MASS point source catalog and the USNO-B1 catalog. NOAO has implemented servers for these catalogs. These use the nice WCSTOOLS/scat tools (http://tdc-www.harvard.edu/software/wcstools/scat/scat.cgi.html) with the addition of an "mradius" parameter to specify a radius in arcminutes. The interface is a direct call to scat with the CGI interface. So you can enter your own scat command if you want. For example:
http://archive.tuc.noao.edu/cgi-bin/scat?catalog=tmc&ra=27.5299361&dec=13.6118889&sys=J2000&mrad=1.0&nstar=-1

I also developed an ASTCAT database entry for the 2MASS PSC catalog through a nicely documented site at the NASA/IPAC Infrared Science Archive. The reference URL is http://irsa.ipac.caltech.edu/applications/Gator/.

The IRAF catdb.dat entries for use with the ASTCAT package are given below. The system file is astcat$lib/catdb.dat. See "help astcat.catalog" for the documentation. For a personal modification you can copy this file, say to your IRAF home directory, and add the new entries. The AGETCAT task has a parameter, which is redirected to an ASTCAT package parameter, which points to the database. So you would just need to change one of these parameter to your modified version and then access the catalog with "usnob1@noao", "twomass@noao", or "twomass@irsa".

If you don't use the filtering features of the ASTCAT tasks you will get all the fields returned from these sites. You can use the filtering to restrict the fields and format them. In that case you would have to modify the "nfields" block to identify fields you might want to filter on. The ones given here are defined to produce celestial coordinates and J, H, K (2Mass) or J, F, N (USNO-B1 photographic) magnitudes.

The new entries will be in the next IRAF release. Also in future releases of external packages that iinclude the task MSCGETCATALOG the database file will be included and directed to that database.

Note that getting coordinates through the IRSA Gator site can be fairly slow; up to several minutes. The NOAO server is much faster.

begin usnob1@noao
address inet:80:archive.tuc.noao.edu:text
query GET /cgi-bin/scat?catalog=ub1&ra=%-s&dec=%-s&sys=J2000&mrad=%-s&nstar=-1 HTTP/1.0nn
nquery 4
    ra 00:00:00.00 hours %0.2h
    dec 00:00:00.0 degrees %0.1h
    radius 6.0 minutes %0.1f
    qsystem J2000.0 INDEF %s
protocol http
type btext
    hskip 12
nheader 1
    csystem J2000.0
nfields 7
    id 1 12 INDEF %12s
    ra 14 12 d hours %12.3H
    dec 27 12 d degrees %12.2h
    mag1 52 4 r INDEF %4.2f
    mag2 58 4 r INDEF %4.2f
    mag3 64 4 r INDEF %4.2f
    dist 90 6 r minutes %6.2f

begin twomass@noao
address inet:80:archive.tuc.noao.edu:text
query GET /cgi-bin/scat?catalog=tmc&ra=%-s&dec=%-s&sys=J2000&mrad=%-s&nstar=-1 HTTP/1.0nn
nquery 4
    ra 00:00:00.00 hours %0.2h
    dec 00:00:00.0 degrees %0.1h
    radius 6.0 minutes %0.1f
    qsystem J2000.0 INDEF %s
protocol http
type stext
    hskip 11
nheader 1
    csystem J2000.0
nfields 7
    id 1 0 INDEF %11s
    ra 2 0 d hours %12.3H
    dec 3 0 d degrees %12.2h
    mag1 4 0 r INDEF %6.3f
    mag2 5 0 r INDEF %6.3f
    mag3 6 0 r INDEF %6.3f
    dist 7 0 r minutes %6.2f

begin twomass@irsa
address inet:80:irsa.ipac.caltech.edu:text
query GET /cgi-bin/Gator/nph-query?outfmt=1&objstr=%-s+%-s&spatial=Cone&radius=%-s&radunits=arcmin&catalog=fp_psc HTTP/1.0nn
nquery 4
    ra 00:00:00.00 hours %0.2h
    dec 00:00:00.0 degrees %0.1h
    radius 1.0 minutes %0.1f
    qsystem J2000.0 INDEF %s
protocol http
type btext
    hskip 19
nheader 1
    csystem J2000.0
nfields 5
    ra 2 10 d degrees %12.3H
    dec 13 10 d degrees %12.2h
    mag1 58 6 r INDEF %6.3f
    mag2 75 6 r INDEF %6.3f
    mag3 92 6 r INDEF %6.3f
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