This attribute controls the generation of FITS-WCS alternate axis keywords by the AST_WRITE method. It determines which of the Frames in the FrameSet supplied to AST_WRITE are used to create a set of alternate axis descriptions. It may be set to one of the following values (case insensitive):

• " ALL" : A set of alternate axes will be created for each Frame in the supplied FrameSet, excluding the Base and Current Frames. This is the default.

• " NONE" : No alternate axes will be created for any of the Frames in the supplied FrameSet.

• " IDENT" : Alternate axes will be created for a Frame only if its Ident attribute is set to a single upper case alphabetical character (A-Z).

FitsChan

• This attribute is used only if the Encoding attribute of the FitsChan is set to (or defaults to) " FITS-WCS" or " FITS-PC" .

• The Current Frame in the FrameSet is always used to create the primary axis descriptions in the output FITS header.

• The Base Frame in the FrameSet is never used to create a set of alternate axis descriptions.