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Decompressing FPacked data

LCO image data is available in a compressed format, using a library called FPack. The advantage is that it reduces the file size by a factor 3.5 but can still be read (without needing to decompress it) by our image pipeline and most astronomical software.

Software which opens .fz files

Problems Using LCO data?

If you cannot use data which has been compressed with FPack you can use the following steps to decompress it back into the conventional FITS format.

LCO Archive Download

The easiest way to obtain uncompressed FITS images is to download them from the LCO archive by selecting "with uncompressed fits files" from the download menu.

Downloading uncompressed FITS from the archive


If you have a copy of DS9 you can use this to convert your images. Open the image ( File > Open...), then save the image as a regular FITS file ( File > Save as Fits).

FITS Liberator

If you are using FITS Liberator, you do not need to unpack the FITS files. Just remove the .fz from the filename, leaving .fits on the end.

Windows 7+

  1. Download the FPack library
  2. Right-click the file once it has downloaded and select "Extract"
  3. Copy all the files you extracted from the file, into the same directory as your data files (the ones which end '.fz')
  4. Double click on the file called funpacker.bat (it might just appear as 'funpacker')
  5. DO NOT USE FPack.exe or FunPack.exe
  6. All the .fz files in your folder should now end in '.fits'

Mac OS X

  1. Open the 'Terminal' application, located in Applications > Utilities > Terminal
  2. Follow the instructions for installing the library CFITSIO (this contains fpack).
  3. You can now type funpack followed by the name of each file ending in '.fz', or you can type "funpack *.fz" to decompress all of them at once.

You can loop through all files in the current directory by typing the following into a terminal:

for file in *.fits.fz; do funpack "$file"; done

If you are still having problems with this please use our help page for assistance.