WCSTools 3.0 More Tools for Image Astrometry and Catalog Searching Douglas J. Mink Smithsonian Astrophysical Observatory

For five years, WCSTools as provided image astrometry for astronomers who need accurate positions for objects they wish to observe. Other functions have been added and improved since the package was first released.

• imwcs has been improved in several ways:
  • Fits may be repeated, with and without tightening the tolerance on matches between image and catalog stars.
  • Any of several magnitudes in a reference catalog can be used to order the brightest stars for matching.
  • A WCS can be fit to an initial set of X/Y/RA/Dec matches, with optional full match and fit of more image stars.

• WCSTools includes and uses Mark Calabretta's latest release of WCSLIB, version 2.7, for projections, and supports multiple world coordinate systems in a single header.

• Catalogs are now searchable over the World Wide Web. The catalog searching routine can be located on either end (or both ends!) of such a web connection, and the output from one catalog search can be used as the input to another search. You can search the HST GSC and the USNO-A2.0 Catalog on the ESO Catalog servers.

• Support has been added for new catalogs, such as the GSC-ACT and 2MASS Point Source Catalog as they have come out. Access over the web to the GSC II Catalog Server at the Space Telescope Science Institute is supported as a default. A simple command line interface can search any supported catalog, returning information in several standard formats.

  Results from IMWCS fits to CCD images of a field in the M67 open cluster and a random field centered on a galaxy are compared for the various applicable catalogs.

• scat has been made to work more like a filter, so the output of a search of one catalog can be used as input for a search of another catalog. It has also been extended so it can be used as part of a web site which serves archived spectra.

The goal of this project is to have a good set of command line tools for dealing with images, their headers, source catalogs, and relationships between them. The FITS WCS standard will be completely supported when it is agreed upon, and access to more catalog-serving web sites will be added in the future.