Long have I pondered the Binary Sunset shot in Star Wars… Here is my definitive Take on what happened and a Color Scheme and a DIY Kit of Matte and Mock up.
This is a sky and Sand Replacement Matte.
Color Scheme for twin suns and fixed Brighter Sun
Mock up of Final Composite. Looks as though the twin suns shots was meant to be integrated into the Shot with Luke. The Scale of the Hill and the Clouds would be correct and this is a color scheme that I also feel makes sense. I think they may have struggled to integrate the twin suns into the live action so It became just plant a fake sun in the shot rather than actually use the Matte shot integrated.
I hope you like it but this shot is now finally settled in my mind.
Scaled different but definitely better bigger or Larger suns than the Original
Reference
Docking Bay 327 Replacement Matte