With this free image converter, you can convert images to fits online. Optional settings can be provided to improve quality.
FITS
.FITS Flexible Image Transport System
What is the FITS format? The FITS file type is primarily associated with FITS. FITS (Flexible Image Transport System) is the data format most widely used within astronomy for transporting, analyzing, and archiving scientific data files. FITS is much more than just another image format (such as JPG or GIF) and is primarily designed to store scientific data sets consisting of multidimensional arrays (images) and 2-dimensional tables organized into rows and columns of information. Often this file will have the extension .FIZ.