Hack a FITs Image Header

Question

I need to change a few values in a couple of FITs image headers to fit with some test data I have. Therefore I'm trying to hack a FITs image header at the minute to run with the application.

However at the minute - I can't even see the header, never mind hack it. I run Ubuntu.

Can anyone advise some software to view the FITs - perhaps even hack it?

Answer 1

Kind of old, but I think the answer could use some updates and additional information.

View .fits file

My personal favorite GUI for viewing '.fits' files is DS9. Once installed you can view a file by typing ds9 /path/to/file.fits. Alternatively you can just use the menu in the GUI to load the image. Once you load the image in the viewer, you can view the header information by using the very top menu bar and going to 'File -> Display Header'. Unfortunately, I dont believe you can modify the header in DS9.

Modify fits header

For modifying the fits header, I found the easiest is to use astropy (a python package). Since you're using Ubuntu you should be able to download it via apt-get, so hopefully pretty easily. To actually edit the fits header, you can do the following in a python script, or from the interpreter (here's some additional help):

# Import the astropy fits tools
from astropy.io import fits

# Open the file header for viewing and load the header
hdulist = fits.open('yourfile.fits')
header = hdulist[0].header

# Print the header keys from the file to the terminal
header.keys

# Modify the key called 'NAXIS1' to have a value of 100
header['NAXIS1'] = '100'

# Modify the key called 'NAXIS1' and give it a comment
header['NAXIS1'] = ('100','This value has been modified!')

# Add a new key to the header
header.set('NEWKEY','50.5')

# Save the new file
hdulist.writeto('MyNewFile.fits')

# Make sure to close the file
hdulist.close()

You could also throw this in a loop for multiple file manipulation.

Answer 2

If you are familiar with the python programming language, you could use the astropy module to view and manipulate fits files. Say you want to view the header of the file 'image.fits', then you do:

from astropy.io.fits import getheader

header = getheader('image.fits') # Load the data
print header                     # Print the header to screen

If you want to modify a particular key of the header, you do:

header['key'] = 'new_key'