There must be many 3rd party freeware IDL libraries for FITS processing distributed on the Internet. All you need to do is enter a Google search for "FITS IDL Library" and you will soon see how many options there are. I would expect that the implementations in the extremely widely distributed 3rd party NASA-originated library "astrolib" would be the most extensively used. Here are a couple of web links that takes you to two web pages on NASA's website that would be particularly pertinent: http://fits.gsfc.nasa.gov...ies.html#idl_fitstab and: http://idlastro.gsfc.nasa.gov/fitsio.html James Jones