[fitsbits] XTENSION = 'FITS' proposal

[Preben Grosbol]

On Wednesday 10 April 2002 23:36, Perry Greenfield wrote:
> Proposal for a "FITS" Extension (XTENSION = 'FITS')

I have some sympathy for a proposal of this kind but it is too limited
in scope.  You may recall that there already is a reserved extension
type XTENSION = 'DUMP' which was intended for binary dumps
(ref. NOST 100-2.0).  One may find a better name for such byte
stream extensions (e.g. 'BSTREAM') but one would sometimes like
to store additional information together with binary data in a FITS
file.  Typical examples would be:
   1) Observing logs in e.g. XML format
   2) Reduction logs in e.g. ASCII text
   3) Binary dumps from an instrument
   4) Graphs in e.g. PostScript format
   5) A paper in e.g. LaTeX format
   6) or as you mention another FITS file.

This would call for an extension like:

  XTENSION = 'BSTREAM '  or 'DUMP    '
  BITPIX = 8
  NAXIS = 1
  NAXIS1 = <size of byte stream in bytes>
  BSTYPE = 'data type'

where 'data type' should be controlled and possibly have values
like 'NONE', 'FITS', 'XML', 'POSTSCRIPT', 'LATEX', 'PDF', 'TEXT'
etc.  For 'TEXT' type, one could add a keyword to give the character
encoding.

 This type of extension would be much more general but still serve
the purpose of providing a hierarchical structure for your FITS files.

Preben Grosbol