Convert fits to pnm Online: fits2pnm

You can use Tom's Editor to easily convert images from
Flexible Image Transport System .FITS to Portable aNy Map .PNM.
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.

PNM

PNM images are uncompressed 24 bit RGB images. Can cannot store Alpha channel. PNM images come in 2 types: binary and text. Especially popular on Linux.