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headers stsdas.toolbox


NAME · INTRODUCTION · HEADER_EDITING

NAME

headers -- Tools for examining & editing image headers.

INTRODUCTION

There are several tasks in this package for examining and editing image headers---particularly GEIS format image headers. Type "help geis" for more information about the data structure for HST data. The `headers' package is implicitly loaded when STSDAS is loaded. Placing these tasks in a separate package merely serves (in this case) to emphasize the logical relationship between them, and to make the package menu small and informative. A quick summary is given in Table 1 below, followed by a few highlights. Utilities for examining, editing, and reformatting images can be found in the `toolbox.imgtools' package.


                Table 1.  Image Header Utility Tasks
  +--------------------------------------------------------------+
  | Task        | Description                                    |
  +--------------------------------------------------------------+
  | eheader     | Interactively edit an image header             |
  | groupmod    | Add/delete group parameters from GEIS images   |
  | hcheck      | Check image header keywords                    |
  | hdiff       | Display differences between two headers        |
  | iminfo      | Print instrument-specific info for HST images  |
  | stfhistory  | Add history records to a GEIS image header     |
  +--------------------------------------------------------------+

HEADER EDITING

There are four tasks in `headers' for editing the contents of an image header.

'eheader'   - Interactive editor for editing all header keywords
              and values, including those in a group parameter block.
' 
          header editor is the 
most general utility, in that it allows the user to edit 
interactively all header keywords and their values, including those 
in a GEIS group parameter block (GPB), but it cannot add or delete 
GPB keywords.  The `chgkeywrd' task provides a non-interactive 
means to change the names (but not the values) of many header 
keywords at once, but it cannot modify the names of GPB keywords 
either.  The `groupmod' task DOES allow keywords to be added to or 
deleted from the GPB, but it initializes them all to only one 
chosen value.  (For more details about GEIS format files, type 
"help geis".)  Finally, the `stfhistory' task will add a text 
string as a "HISTORY" record to an image header.  
.ih
HEADER EXAMINATION
There are three tasks for examining the image header contents.  The 
`iminfo' task prints the values of some generally useful keywords 
that are found in most astronomical image headers, such as the 
image size, the integration time, the RA & Dec, UT and ST, etc.  
For HST data this task will print various, instrument-specific 
information, such as the filter(s)/grating(s) used, the instrument 
operating mode, etc.  The two more general tasks are `hdiff', which 
prints the names and values of keywords that differ between pairs 
of images, and `hcheck' which will print the values of specified 
keywords based upon a user-specified condition.  `hcheck' is quite 
general and is very useful for finding keyword values that are, 
e.g., out of range, or missing altogether.  
.ih
GROUP FORMAT IMAGES
Users should be aware that modifications to GPB keywords must be 
performed explicitly on each group in multi-group GEIS files; the 
default is to operate on only the first image group.  To learn the 
syntax for operating on individual image groups, type "help geis". 
.ih
SEE ALSO
toolbox.imgtools.  

Type "help geis" for more information about GEIS format files.  
.bp
.endhelp



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