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.

Montage 3.3                                         June 2010                                      MSHRINKHDR(1)