Convert fits to dds Online: fits2dds

You can use Tom's Editor to easily convert images from
Flexible Image Transport System .FITS to Direct Show Surface .DDS.
Tom's Editor is a free, online image manipulation and converter program.

Go to Tom's Editor

FITS

Flexible Image Transport System is an image format with extension FITS.

DDS

DDS are files invented by Microsoft to be used in games, mostly as textures. Images can be compressed to save space but the compression methods defined by DDS are all very fast in terms of coding and decoding.