FITS header

Keywords contained in the header of a FITS file can be displayed in Siril. To do this, simply click on Tool ‣ FITS Header.

Since version 1.3.0, it is possible to modify the value of keywords supported by Siril, either with the update_key command, or via the GUI, in the appropriate window. This window is divided into two tabs. The first, the Header Editor, is active for single images, out of sequence. It may vary from what the file header actually looks like, and represents more the state it will be in after saving. Keyword values are updated in real time. The second tab displays the header in text format as written in the file and as it was represented for Siril versions below 1.3.0.

Warning

HISTORY keywords are not displayed in the editor. They are visible in the Saved Header tab.

Another way of displaying the header is to use the command line dumpheader. It shows the same header as displayed in the Saved Header tab.

Warning

As SER files contain very few keywords and are different from FITS files, this command is not applicable to this type of sequence.

Key name, key values and key comments can be modified, however, the key must be unprotected. For easy recognition, protected keys are displayed in salmon color.

Editing is very simple, just double-click on the cell to be modified. The first time selects the field, the second opens the edit mode. Pressing the Enter key validates the entry. To make the changes effective, remember to save the file.

Warning

Please note that Siril does not check the validity of the value entered. It is up to the user to enter a valid value. An incorrect value may lead to undesirable behavior in Siril's keyword processing.

FITS Header dialog when editing the value of a keyword.

Second tab of the FITS Header dialog.

The window contains an option in the form of a Copy selection button. It copies the selected lines to the clipboard in the original format of the FITS header, and works for both tabs.

Finally, you can add a new keyword using the + button at bottom left, and delete one using the - button:

1. To add a keyword, click on the + button. A new dialog box opens, as shown below. This window lets you add a new keyword, whose name will be limited to 8 characters (the HIERARCH convention is not used). You can leave the Comment field empty, if the other two are filled in. However, the user can only fill in the Comment field to add a single comment to the FITS header. Finally, if the keyword exists, then its value will be updated with the information provided.

   

   The window for adding new keywords.

2. To delete a keyword, select one or more lines and click on the - button (or with the keys Del or Backspace). The selected keywords will be deleted, unless they are protected.

   Tip

   When a sequence is loaded, it is only possible to select one line at a time. This means you can only delete one keyword at a time from a sequence. But for a single image, you can select several.

Siril command line

dumpheader

Dumps the FITS header of the loaded image in the console

Siril command line

update_key key value [keycomment]
update_key -delete key
update_key -modify key newkey
update_key -comment comment

Updates FITS keyword. Please note that the validity of value is not checked. This verification is the responsibility of the user. It is also possible to delete a key with the -delete option in front of the name of the key to be deleted, or to modify the key with the -modify option. The latter must be followed by the key to be modified and the new key name. Finally, the -comment option, followed by text, adds a comment to the FITS header. Please note that any text containing spaces must be enclosed in double quotation marks

Siril command line

sequpdate_key sequencename key value [keycomment]
sequpdate_key sequencename -delete key
sequpdate_key sequencename -modify key newkey
sequpdate_key sequencename -comment comment

Same command as UPDATE_KEY but for the sequence sequencename. However, this command won't work on SER sequence

Links: update_key