Flexible Image Transport System (FITS) data is an agreed file format for the storage of scientific imaging and is fully endorsed by both NASA and the IAU. FIT is more useful to scientists than JPG or BMP formats as it allows for data sets to be stored which consist of multi-dimensional arrays. Examples of common uses include 3D representations of brain scans, or Red Green Blue and Luminescence (RGBL) channels in astrophotography. Each data set can be extracted and processed separately, then combined to form a standard image.
By using FIT images with digital imaging, you have separate data for each channel which increases signal to noise ratio, improves image quality and allows enhanced image post-processing flexibility.
Many professional astronomers use CCD imaging devices which output FIT data. The Hubble Space Telescope also transmits FIT data to be processed by NASA/ESA back on Earth. The Sloan Deep Space Survey has mapped out most of the sky in FIT format as well.
If you were to look at a Hubble FIT image, you would be very disappointed with the quality and colour of the image. FIT images require a lot of post processing to become acceptable. Each channel in a FIT image has to be rotated, aligned and processed separately before finally being combined to the spectacular end result we see in the press.
To streamline the process NASA and the ESA (European Space Agency) have developed a plugin for Photoshop called FITS Liberator, which strips down the layers of a FIT and imports them to Photoshop for processing. There are a few other tools available as well, which again are available from NASA.