If a coordinate system with the same Domain (name) already exists it will be overwritten, and a warning message issued.
AST files for use by this program will normally be those written by the ASTEXP program, and may either be standard ones designed for use with a particular instrument, or prepared by the user.
It is intended that this file should be one written by the ASTEXP application when a successful registration is made, and the user need not be aware of its internal structure. The files are readable text however, and can in principle be written by other applications or doctored by hand, if this is done with care, and with knowledge of AST objects (SUN/210). The format of the file is explained in the Notes section.
It will normally not be necessary to supply this keyword, since it can be given instead within the AST file. If it is supplied however, it overrides any value given there. [!]
If the logging system has been initialised using CCDSETUP, then the value specified there will be used. Otherwise, the default is "CCDPACK.LOG". [CCDPACK.LOG]
The AST file consists of the following, in order:
frameset 1 modifiers
frameset 2 modifiers
(end of file)
Characters after a '#' character are normally ignored. The constituent parts are composed as follows:
A single blank line, which may contain spaces but no comments.
The framesets are written in AST native format, as explained in SUN/210.
Each frameset has an ID, and contains two frames (a Base frame and a Current frame) and a mapping between them. The domains of all the Base frames should normally be the same, and likewise for all the Current frames. For the images to which the file will be applied by ASTIMP, their WCS components should contain frames in the same domain as the AST file's Base frame.
The ID of each frameset is used to determine, for each image, which of the framesets in the file should be applied to it. This ID is a string which can assume one of the following forms:
USE keyword argumentsCurrently the only modifier defined is FITSROT, which defines the name of a FITS header which specifies how many degrees to rotate the image before use. This rotation is carried out after the mapping defined by the frameset itself.
Global modifiers affect all images processed with the AST file. Frameset modifiers affect only those images which correspond to their frameset.
Rigorous error checking of the AST file is not performed, so that unhelpful modifications to the WCS components of the target images may occur if it is not in accordance with these requirements.
Retaining parameter values has the advantage of allowing you to define the default behaviour of the application but does mean that additional care needs to be taken when re-using the application after a break of sometime. The intrinsic default behaviour of the application may be restored by using the RESET keyword on the command line.
Certain parameters (LOGTO, LOGFILE and NDFNAMES) have global values. These global values will always take precedence, except when an assignment is made on the command line. Global values may be set and reset using the CCDSETUP and CCDCLEAR commands.