When Rahu Graha Yuti joins forces with Chandra or Surya Graha in a Kundali, Grahan Yog is created. Chandra Rahu Grahan Yog is what is created when Rahu and Chandra Yuti come together. Surya Rahu Grahan Yog is what is created when Surya and Rahu Yuti come together.