FIT is better known as FITS (short for Flexible Image Transport System) and an image format widely used for saving and storing the images grabbed using telescope observations.
The FIT format was created for storing astronomical image data using a standard format, and it contains both binary data and ASCII text.
The image converters that feature with built-in support for this specific graphic format will allow users to export their own images to FIT.
Some of these tools will also offer users the option to perform various basic editing onto the source image files, such as rotate, crop, or adjust their color and brightness.