NAME

       mShrinkHdr - Make a FITS header from a template with different pixel scale

SYNOPSIS

       mShrinkHdr [-d][-s scale] template.hdr shrunken.hdr

DESCRIPTION

       There  are  two  ways  to  generate "thumbnail" images.  One is to build a full-resolution
       mosaic and shrink it down using mShrink to the scale desired.  This process can be  costly
       if  the  full  resolution image is not desired (or not desired yet).  It is much faster to
       mosaic at the scale of the thumbnail itself.  One  reason  for  doing  this  could  be  to
       evaluate whether th full-resolution mosaic is worth building at all.

       mShrinkHdr  is  a simple utility that takes a FITS header template (such as might come out
       of mMakeHdr or mHdr) and make a new one at a differenc pixel scale.  The default scale for
       this new header is 200 pixels, though the user can override this with any value.

OPTIONS

       -d

              Turn on debugging.

       -s scale

              Set the size in pixels of the larger axis.

ARGUMENTS

       template.hdr

              Original FITS header template.

       shrunken.hdr

              "Thumbnail" FITS header template.

RESULT

       If  successful,  the  result  is  a  new  FITS header template with a size and pixel scale
       appropriate to making a thumbnail mosaic.

MESSAGES

       ERROR  Cannot open output template file

       ERROR  Bad template: filename

       ERROR  Output wcsinit() failed.

EXAMPLES

       $ mShrinkHdr region.hdr thumbnail.hdr
              [struct stat="OK"]

BUGS

       The drizzle algorithm has been implemented but has not been tested in this release.

       If a header template contains  carriage  returns  (i.e.,  created/modified  on  a  Windows
       machine),  the cfitsio library will be unable to read it properly, resulting in the error:
       [struct stat="ERROR", status=207, msg="illegal character in keyword"]

       It is best for the background correction algorithms if the area described  in  the  header
       template  completely encloses all of the input images in their entirety. If parts of input
       images are "chopped off" by  the  header  template,  the  background  correction  will  be
       affected.  We  recommend  you  use  an expanded header for the reprojection and background
       modeling steps, returning to the originally desired header size for the final  coaddition.
       The default background matching assumes that there are no non-linear background variations
       in the individual images (and therefore in the  overlap  differences).  If  there  is  any
       uncertainty  in  this  regard, it is safer to turn on the "level only" background matching
       (the "-l" flag in mBgModel.

COPYRIGHT

       2001-2015 California Institute of Technology, Pasadena, California

       If your research  uses  Montage,  please  include  the  following  acknowledgement:  "This
       research  made use of Montage. It is funded by the National Science Foundation under Grant
       Number ACI-1440620, and was previously  funded  by  the  National  Aeronautics  and  Space
       Administration's  Earth Science Technology Office, Computation Technologies Project, under
       Cooperative Agreement Number  NCC5-626  between  NASA  and  the  California  Institute  of
       Technology."

       The  Montage  distribution  includes an adaptation of the MOPEX algorithm developed at the
       Spitzer Science Center.