Find USNO-B1.0 Stars in Image Region

WCSTools programs
imua2 is a link to the WCSTools imcat utility which finds all of the U.S. Naval Observatory B-1.0 Catalog objects in a FITS or IRAF image and lists their sky and image positions. World coordinate system (WCS) information must be present in the image header to describe, in a standard way, the relationship between sky coordinates and image pixels. This information is used by the program to find the region in the sky to search and to transform right ascension and declination sky coordinate pairs to image coordinate (X,Y) pairs. Output is sent to a file called filename.uac and to standard output if the -v flag is set. The UA2 number is the zone ((90 + declination in degrees) * 10) followed by the sequence number of the star within the RA-sorted zone. This number will change with each release of the USNO A catalog.

Before you can use this program, the path to the directory containing the region files must be set. The default is to use the value of the variable ub1path in the source code file libwcs/ubcread.c, which is initially set to /data/ub1, which is where the catalog resides at the Center for Astrophysics. If you do not have access to the source code and need to change the path, you can set the environment variable UB1_PATH to the directory containing the region files, and that will override the file setting.

The minimum command line is imub1 FITS or IRAF filename

The same effect can be obtained by running imcat -c ub1 FITS or IRAF filename

Command Line Arguments

There are two USNO-B1.0-specific parameters which can be set on the command line. If they appear, they must come after -c ub1 or imub1 on the command line.
minid=number If the object is found on fewer than this many plates, where the range is 2-5, it is left off the list. All Tycho-2 stars, where the catalog value of this number is set to zero, are included unless number is negated. The default value set in the file libwcs/ubcread.c is 0. For the most accurate positions, use minid=4.
minpmqual=number If the proper motion quality flag is less than this number, proper motion is never added to the catalog position. The range is 1-9 from the catalog, or 10 if the proper motion is from the Tycho-2 Catalog. Setting this to 11 will never add proper motion. The default value set in the file libwcs/ubcread.c is 3. For the best proper motions, use minpmqual=9.


List the 10 brightest USNO-B1.0 Catalog stars in a FITS image from a CDROM
List the USNO-B1.0 Catalog stars in a FITS image to a file
Plot USNO-B1.0 Catalog stars onto a FITS image

Last updated 6 October 2003 by Doug Mink dmink@cfa.harvard.edu

Telescope Data Center