Configuration of mask generation software

  In addition to all the data about the observation provided by the user,
the software needs information about the instruments themselves, and the
environment in which it is running.  Sometimes these things will change
and need to be updated for best performance, or for certain special uses.
Here is where to find these other data.

  For most definition and data files, the mask generation software will look
for the named file in the local directory, and two generations of parent
directories; then in a directory specified by an environment variable, and
finally in the special directories /usr/local/etc/maskcut/, /usr/local/etc/maskgen/
and /usr/local/etc/ for the file or a symbolic link.  It is usual for the
software to be installed with the actual distribution file symbolically linked
from /usr/local/etc or /usr/local/etc/maskgen.  Also, an environment variable
may be defined to point to the directory for each data file.

  As a new feature, the Environment Variable MGPATH may be defined as a colon
separated list of directories, and this list will be searched for most files
to be opened for input by the Mask Generation software programs.  This will
include all configuration data, and all user input data.  The star catalog
files use a separate CATPATH which is also a colon separated list for finding
the star catalog root directory.  The catalog data cache uses the local
directory or the single directory specified by CATCACHE to hold its data.


    Data for the sky window feature:
  To aid in obtaining a proper guide star, the sky window shows the IMACS
(or other) instrument field on the sky with catalog stars.  The sky catalog
used is a 4 gigabyte subset of the USNO catalog which most users have obtained
from a DVD or by download.  For downloading instructions, see the web page 
  http://users.obs.carnegiescience.edu/clardy/imacs/maskmaking.html 
for a link to the instructions.

  The star catalogs are installed in a directory on a large, fast disk, and
that directory is usually symbolically linked from /usr/local/etc/gcats.
If that is not convenient, the environment variable CATPATH should be defined
to the directory where the catalogs are stored, or alternately the environment
variable GMAPCATS may also be used.  CATPATH may be a colon separated list
of directories to search; the one containing "usno-o" will be used.

  Sky window also needs the file "pmap.dat" which is usually linked from the
common locations above, or its directory may be specified by the environment
variable DEFAULTS; it is also searched for in the MGPATH list.

  The Digitized Sky Survey query facility uses a command which is usually set
to a common web browser, such as firefox.  If you want to use a different one,
such as the ImageMagick "display" command, it may be defined by the environment
variable MYDISPLAY.  The command used must be able to take a general URL as
a command line argument, and handle a returned GIF image or HTML error message.


    Optical definitions file:
  The file opticdef.dat contains all the definitions of the optical
components of the telescope and the instruments.  It is where data for new
instruments is added, and new components such as new dispersers are added.
Therefore, it is distributed with each new edition of the software.  It is
a plain text file and could be edited if you know what you are doing.
However, if changes are needed, a new file will be supplied.

  To read the file, the program checks in the common locations specified
above, and looks for the environment variable "OPTICDEF" to contain the 
directory where opticdef.dat is present.  Also the MGPATH is scanned.
If not found in any of these places, mask generation will fail.


    IMACS rotator offset angle:
  When the IMACS instrument is attached to the instrument rotator, the angle
at which it is clamped can vary slightly.  Although this angle is usually
the same, it could change.  To allow for this, the environment variable
IMACSCHUECO may be defined to the rotator offset angle value in degrees
if needed.  This affects the display of the rotator angle conflict in the
intgui planning display.  It is normally not defined, and the default angle
in the program is used.


    Mask cutting configuration file:
  The file maskcut.cfg contains definitions for the mask cutting machine
and for each kind of mask and mask blank used.  This information is needed
for mask cutting and must be accurate.  This file is distributed with the
software at each release and often contains important new information and
updates.  It is a plain text file, and could be edited if necessary, however
if changes are needed a new file will usually be supplied.

  To read the file, the program checks in the common locations specified
above, and looks for the environment variable "CUTDEF" to contain the 
directory where maskcut.cfg is present.  Also MGPATH is scanned for it.
If not found in any of these places, mask cutting and ncplot will fail.