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Editing the FITS Header
This topic describes how to edit the FITS header
contents using either the
FITS Header Editor or the
FITS Header Pane. Most Mira commands update and
change it as necessary to keep track of what is done to the image.
However, there will be occasions when you need to manually change
something in the image header. This topic describes how to edit the
FITS Header.
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NOTE
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Lines in the header table that are tinted light red
cannot be changed. For some of these keywords, there are other ways
to change them. For example, NAXIS1
defines the number of image columns. This value can be changed by
the
Crop Image command but changing NAXIS1 here could render the image unreadable.
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How to Undo Changes
Mira preserves 1 level of Undo each time you
change a cell in the table. To recover the previous cell content,
click the  button on the lower left corner of
the window or use the Undo command in the Context Menu (see
below).
Typing New Keyword Data
To change the contents of a particular keyword
line, the simplest procedure is to directly edit the value
or comment cell in the table. Editing a cell is
straightforward. Read through the following procedure once before
following it step by step so that you understand the available
options.
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Bring the cell of interest into view using the
arrow keys, scrollbars, or by resizing the window.
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Double click the mouse on the cell to enter
edit mode. This highlights the entire line and leaves the
insertion cursor at the end. Do not type anything yet!
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If the entire line is highlighted, typing any
character deletes the entire content of the cell. This is
equivalent to hitting the [Delete]
key.
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To position the insertion cursor to a
specific position, click the mouse pointer on the location.
continue typing from there.
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When you are finished typing, exit the
cell using the keyboard Up and Down arrow keys or click the
mouse in a different cell.
Using the Context Menu for More Complex Tasks
To do more than simple editing, Mira provides extra
commands in the FITS Header Context Menu shown below. This
menu opens by right clicking anywhere inside the window.
Most of these commands are self explanatory. Their
use is described in the table below.
FITS Header Context Menu Commands
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Undo (optional)
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The Undo command appears only after a change is
made. Click it to undo your changes to the cell.
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Insert Line
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Inserts a new, blank line at the point of the
cursor and activates the editor in the Keyword cell.
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Delete Line
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Deletes the line at the cursor.
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Rename Keyword
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Opens a list of keywords that Mira knows.
Procedure: Position the cursor on the target
keyword and right click to open the Context Menu. Choose
Rename Keyword to open the list box
of known keywords. Select a new keyword. Mira replaces the cell
with the new keyword name.
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Insert Keyword
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Inserts a keyword from those that Mira knows.
Procedure: Position the cursor where you want to
insert a new keyword line and right click to open the Context Menu.
Choose Insert Keyword to open the
list box of known keywords. Select a new keyword. Mira inserts the
keyword name into the Keyword cell
and moves the cursor to its Value
cell. To edit the value cell
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Insert Blank
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Inserts a blank line with no keyword, value, or
comment. Use this as a spacer to make the header more readable.
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Insert History
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Inserts a HISTORY
keyword line at the point of the cursor. Your text may span both
the VALUE and COMMENT fields of the header.
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Insert Comment
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Inserts a COMMENT
keyword line at the point of the cursor. Your text may span both
the VALUE and COMMENT fields of the header.
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Save your changes
Changes to the FITS header(s) do not take effect
until you have accepted them by clicking a button. These changes
apply only to the displayed image.
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NOTE
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Header changes affect only the displayed
image. To make the changes permanent in the FITS file, you must
save the image using the File > Save command or an
equivalent.
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Related Topics
Working with the FITS image header
FITS Header Editor
List HISTORY Keywords
List COMMENT Keywords
List WCS Keywords
Mira Pro x64 User's Guide, Copyright Ⓒ 2023 Mirametrics, Inc. All
Rights Reserved.
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