## Changes Introduced in V1.8-13

The following describes the most significant changes which occurred in the AST library between versions V1.8-8 and V1.8-13:

1. The FitsChanFitsChan class has been modified so that LONPOLE keywords are only produced by astWriteastWrite when necessary. For zenithal projections such as TAN, the LONPOLE keyword can always take its default value and so is not included in the FITS header produced by astWrite. Previously, the unnecessary production of a LONPOLE keyword could prevent FrameSets being written out using encodings which do not support the LONPOLE keyword (such as FITS-IRAF).

2. The FitsChan class has been modified to retain leading and trailing spaces within COMMENT cards.

3. The FitsChan class has been modified to only use CTYPE comments as axis labels if all non-celestial axes have unique non-blank comments (otherwise the CTYPE keyword values are used as labels).

4. The FitsChan class has been modified so that it does not append a trailing “Z” character to the end of DATE-OBS keyword values.

5. The FitsChan class has been modified to use latest list of FITS-WCS projections, as described in the FITS-WCS paper II, “Representations of celestial coordinates in FITS” (Calabretta & Greisen, draft dated 23 April 2002). Support has been retained for the polynomial correction terms which previous drafts have allowed to be associated with TAN projections.

6. The WcsMapWcsMap class has additional projection types of AST__TPN (which implements a distorted TAN projection) and AST__SZP. The AST__TAN projection type now represents a simple TAN projection and has no associated projection parameters. In addition, the usage of projection parameters has been brought into line with the the FITS-WCS paper II.

7. The WcsMap class has been modified so that a “get” operation on a projection parameter attribute will return the default value defined in the FITS-WCS paper II if no value has been set for the attribute. Previously, a value of AST__BAD was returned in such a situation.

8. The FrameFrame class has new attributes Top(axis)Top(axis) and Bottom(axis)Bottom(axis) which allow a “plottable range” to be specified for each Frame axis. The grid produced by the astGridastGrid method will not extend beyond these limits.