NAME:
  mknicsky
 PURPOSE:
  Create a master sky image from a set of dithered NICMOS images.
 DESCRIPTION:

 CATEGORY:
  CCD data processing
 CALLING SEQUENCE:
  mknicsky,root,PATH=path,OUTPATH=outpath
 INPUTS:
  root - Root of observation set.  This is usually a 6 character name, the
            first 4 characters identify the proposal id and the last two
            identify the visit.
 OPTIONAL INPUT PARAMETERS:

 KEYWORD INPUT PARAMETERS:
  path    - Directory where the images are read from.  (default = current)
  outpath - Directory where the final sky image is to be written to,
               (default=path)
 OUTPUTS:

  A FITS file is written to "outpath" with the name, root_.sky
    where  is replaced by the grism name as read from the header.
    Note that you must have at least 3 images for a given grism for the
    sky image to be created for that grism.

 KEYWORD OUTPUT PARAMETERS:

 COMMON BLOCKS:

 SIDE EFFECTS:

 RESTRICTIONS:

 PROCEDURE:

 MODIFICATION HISTORY:
  Written by Marc W. Buie, Lowell Observatory, 1999 July 12
  2004/9/21, MWB, removed obsolete call to Findfile