All successful use of AST_READ
on a FitsChan is destructive, so that FITS header cards are consumed in the process of
reading an Object, and are removed from the FitsChan (this deletion can be prevented for
specific cards by calling the FitsChan
AST_RETAINFITS routine). An unsuccessful call of
AST_READ (for instance, caused by the FitsChan not containing the necessary FITS headers cards
needed to create an Object) results in the contents of the FitsChan being left unchanged.
The AST Object returned by a successful use of AST_READ on an StcsChan, will be
either a
Region or a
KeyMap, depending on the values of the
StcsArea,
StcsCoords and
StcsProps attributes. See the documentation for these attributes for further information.