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.