Subject: Fits Formats

From: [email-masked] (Midnight A)
Date: 9 Dec 1994 15:45:22 -0500

Since each pixel of an image have to be
represented by a couple of letters (1 letter = 8 bits = 1 byte), imagine
the length of a message consisting of an image being transformed into
characters (UUencoded). That is why images will not be tolerated in this
echo as in most others.

FITS is the "defacto" standard among astronomers for exchanging
information. Not only images but catalogs also! Look at the following
paragraphs that are from the ADC (Astronomical Data Center):

        The ADC is currently working on a second ADC CD-ROM. The first
        CD-ROM has been very successful, with over a thousand copies
        distributed to date. The first ADC CD-ROM contained both ascii
        and FITS versions of catalogs. The  FITS headers were designed
        to be homogeneous over the CD-ROM. In  particular, the labels of
        the fields, and the comments were used to  insure that
        uniformity.

        Since the creation of the first ADC CD-ROM, the ADC has worked
        with  the CDS in Strasbourg to come to a common way of
        documenting the  (tabular) catalog data. The advantages of that
        approach are many since  the CDS and ADC regularly exchange
        their catalogs and try to maintain  mirror archives. The
        approach adopted was designed by Francois  Ochsenbein at CDS.
        The basic documentation allows the user to read a  simple
        document description and the automatic creation of FITS  files
        from the catalog files. The data and documentation can therefore
        be archived as flat ascii files. This removes the requirement to
        keep  both ascii and FITS versions in the archive. Only one data
        file has to be maintained (thus simplifying error corrections
        etc.), and premium disk space is saved. The easy readability of
        the basic documentation files means that a browse capability
        through the World Wide Web is easily implemented using
        wais-indexing, etc.

        (stuff deleted...) All catalogs will conform to the version 1.5
        of the documentation standard. This means the basic
        documentation files (ReadMe) for each catalog will contain all
        information necessary to  build a FITS file automatically.
        Currently, we need to decide whether to distribute the catalogs
        in FITS only, in ascii with fits headers separately, or both in
        ascii and FITS. We need some input from our user community --
        that means you!  We've included a short questionnaire with this
        article. Please take the time to fill it in and return it as
        indicated.

        (Stuff deleted...)

        We plan to include Lee Brotzman's Fits Table Browser software.
        Is there any other FITS table browser that should be included ?
        We would like to hear from you. We are considering putting files
        in hypertext markup language on the CD-ROM so that the Mosaic
        client can be used to browse the disk. We are not able to
        distribute the NSCA clients on the CD-ROM because of licensing
        agreements of the UoI. Any suggestions in this area are also
        very welcome.

See? In the last paragraph, they talk about a Fits Table Browser
software... It is the same for images. You will need a software built to
handle such files. Personnally, i use MiPS (the Microcomputer Image
Processing System) and PRISM that are used in professionnal
observatories. Expect to pay 300-400$ for each. Also, i don't know much
other softwares that can handle Fits format.

That is why most of amateur astronomers distribute their images in the
proprietary format of their CCDs or in TIFF format that is a second
choice after FITS because it loose less information than the GIF format
that drops information for compression purposes.

For example, the CCD-Quebec magazine (w/disks) distribute images in
their native format and frequently suggest enhancing methods to apply to
these just as you mentioned.

So, as you said, it is really a possible thing to do and a good way to
go because that way, no one is stuck with a "badly" transformed image
and it is possible to enhance details the way he/she wants.

 [email-masked]