## Changes Introduced in V3.3

The following describes the most significant changes which have occurred in the AST library between versions V3.2 and V3.3:

1. Options have been added to the SkyFrameSkyFrame class which allows the origin of celestial coordinates to be moved to any specified point. See the new attributes SkyRef, SkyRefIsSkyRefIs, SkyRefP and AlignOffsetAlignOffset.

2. An option has been added to the FitsChanFitsChan class which allows extra Frames representing cartesian projection plane coordinates (“intermediate world coordinates” in the parlance of FITS-WCS) to be created when reading WCS information from a foreign FITS header. This option is controlled by a new attribute called IwcIwc.

3. The FitsChan class which been modified to interpret FITS-WCS CAR projection headers correctly if the longitude reference pixel (CRPIX) is very large.

4. The FITS-AIPS++ encoding in the FitsChan class now recognised spectral axes if they conform to the AIPS convention in which the spectral axis is descirbed by a CTYPE keyword od the form "AAAA-BBB" where “AAAA” is one of FREQ, VELO or FELO, and “BBB” is one of LSR, LSD, HEL or OBS. Such spectral axes can be both read and written.

5. The FitsChan class now has a FITS-AIPS++ encoding which represents WCS information using FITS header cards recognised by the AIPS++ project. Support for spectral axes is identical to the FITS-AIPS encoding.

6. The organisation of the AST distribution and the commands for building it have been changed. Whereas AST used to be built and installed with `./mk build; ./mk install`, it now builds using the more standard idiom `./configure; make; make install`. The installation location is controlled by the `--prefix` argument to ./configure (as is usual for other packages which use this scheme). Note that the INSTALL environment variable now has a different meaning to that which it had before, and it should generally be unset. Also, there is no need to set the SYSTEM variable.

7. Shared libraries are now installed in the same directory as the static libraries. In addition, links to sharable libraries are installed with names which include version information, and “libtool libraries” are also installed (see `http://www.gnu.org/software/libtool/manual.html`).

8. The `ast_dev` script has been removed. Instead, the location of the AST include files should be specified using the -I option when compiling.