FITS vs. CR3 file

Can someone explain why my RAW .cr3 (from Canon EOS Ra ) are 32Mb while the .fit file is 59Mb?
Recently I started capturing both (after a night of accidently capturing only .fits).
I’ve processed both and can see no difference in image quality or stacking (in APP) speed. Folks in my astrophotography club say the difference is header information - but that’s a LOT of header information!
Is there something hidden in the .fit files that I should be taking advantage of, or am I just wasting disk space by collecting both??

@SBeers

This is probably related to bit depth of the files. CR3 files are 14bit files and FITS are 16 bit files.

If APP is your imaging processing choice and APP can use CR3 through out its processing, then there is no reason to create FITS files. APP can save the finished image at either a FITS or TIFF, I believe.

Charlie

@chasmiller46 is correct here. We perform a lossless conversion from 14-bit to 16-bit in order to meet the requirements of the FITS standard. Then, FITS files require some semblance of “filler” data at the end of rows. Finally, the rest may me attributed to header information (but, as you noted, that is not typically 30MB).

Ken, @chasmiller46 - Thank you! Yes, APP is my preferred stacking SW tool (which does save in both .fits and .tiff) - then I take the .tiff stack into Photoshop for the rest of my processing - so no need for the .fits. Appreciate the help and clarification!

Suzanne