Image World Coordinate Setting Program

imwty2 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.

imwty2 uses the Tycho-2 Catalog, an updated version of the Hipparcos Tycho Catalog containing two-and-a-half times as many stars, 2,539,913, with positions and proper motions. The 2MASS Point Source Catalog (imwtmc), with 155,569,249 stars, and the GSC II Catalog (imwgsc2), with 455,851,237 stars, are recent epoch catalogs without proper motions, if you need more stars. The USNO-A2.0 catalog (imwua2) also has a lot of stars (526,280,881), but is based on plates taken in the 1950's, so its accuracy has been decreased by proper motion of its stars.

A set of image stars may be hand-matched to sky positions and used to get a WCS or set initial values for a reference catalog-based WCS (See example).

Command Line Arguments


Using SExtractor to find stars in an image

Find image WCS using HST Guide Stars as references

Find image WCS using pre-matched stars and USNO-A2.0 Stars

Last updated 17 December 2009 by Doug Mink Telescope Data Center [WCSTools Programs]