Image World Coordinate Setting Program

WCSTools Programs
imwub1 is an alias for imwcs, a program which sets the world coordinate system (WCS) of a FITS or IRAF image. The WCS is the relationship between sky coordinates and image pixels and can be described in a standard way in the header of an image. The program was originally written at the University of Iowa, but has been adapted and amplified by Doug Mink at the Smithsonian Astrophysical Observatory.

imwub1 uses the US Naval Observatory B1.0 catalog, which contains 1,036,366,767 stars, which should provide a good number of reference stars for any image.

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 imwub1 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.


Using SExtractor to find stars in an image

Find image WCS using USNO-B1.0 Stars as references

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

Telescope Data Center