README for findzo.sl (ISIS functions) and tg_findzo (CIAO or unix
       command-line wrapper):

0. Purpose: centroid the Chandra grating/acis zero order image using
   the acis frame-shift streak, in cases when the zero order itself
   has been blocked from telemetry, or is distorted by pileup, in
   which cases the CIAO tool, tgdetect, fails.  The zero order
   centroid is needed by CIAO's grating data processing tools.

   See http://space.mit.edu/cxc/analysis/findzo/index.html
   for detailed usage, examples, and download.

1. Requirements for findzo.sl and tg_findzo

	  findzo.sl:  primary function definitions;
	              can be loaded for ISIS interactive use

	  tg_findzo: wrapper script to run as a CIAO tool (CIAO
	             versions 3.4 and higher) or as an ISIS
	             non-interactive script from the unix prompt.

Please install ISIS if it is not available already in your network.
(http://space.mit.edu/cxc/isis/)

If CIAO is installed and it comes with a fully compiled version of
ISIS, it is not necessary to reinstall ISIS.

  CIAO: http://cxc.harvard.edu/ciao/

  Note: In future versions of CIAO ( later than 4.0 Beta 1 ), isis may
  be bundled in the analysis "scripts" software package.  ISIS is NOT
  included in CIAO 4.0 Beta 1.

2. Installation instructions

   - Untar the tar file (which includes this README file).
     E.g.

       > tar xzvf findzo.tgz

   This will unpack into a directory called "findzo-files"       .

   For findzo.sl use only:

   - Copy findzo.sl to the working directory or your ISIS script
     directory and load it into ISIS for use (see examples).

   For tg_findzo (as a CIAO tool or from the unix prompt),

   - Create a directory to store ISIS scripts (e.g.,
     ~/lib/isis/scripts).

   - Create an ISIS initialization file ".isisrc" under your home
     directory, ~/.isisrc (one comes with isis).

   - Set up an ISIS load path in .isisrc file, e.g., 

	variable lpath = "/home/user/lib/isis/scripts" ;
        add_to_isis_load_path( lpath ) ;
        autoload( "findzo", "findzo.sl" ) ;

     to load findzo.sl at every time you execute the "findzo" command
     in ISIS.

     (This convenience will allow you to use findzo.sl in ISIS without
     copying findzo.sl to your working directory.)

   - To use tg_findzo with CIAO, copy tg_findzo.par file to two
     places: your cxcds_param dir (where you keep your CIAO parameter
     files) and $ASCDS_INSTALL/param dir (which may require a
     superuser permission).

     Then copy the S-Lang script tg_findzo needs to be copied either
     to $ASCDS_INSTALL/bin or somewhere under your unix executable
     path.

   - tg_findzo depends on the availability of isis-script (which is
     installed with isis) and by default, /usr/bin/env.  It is
     possible that your system does not have /usr/bin/env. If not,
     please replace the top line of tg_findzo with an appropriate
     pointer to isis-script in your system. For most of linux
     platforms tested for the scripts, this edit has not been
     necessary.

If you have any difficulty with installation or use, please contact us
at bish@cora.nwra.com and/or dph@space.mit.edu for more assistence.

Kazunori "Bish" Ishibashi and David Huenemoerder