I keep an updated list, I think it is accurate.

Grade 1 Coruscant (Pub), Dromund Kaas (Imp)
Grade 2 Taris (Pub), Balmorra (Imp), Nar Shaddaa (Both)
Grade 3 Alderaan, Tatooine
Grade 4 Balmorra (Pub), Taris (Imp), Hoth (Both), Quesh (Both)
Grade 5 Belsavis, Voss
Grade 6 Corellia, Illum
Grade 7 CZ-198, Makeb, Oricon
Grade 8 Rishi, Yavin, Ziost
Grade 9 Darvaniss, Zakuul
Grade 10 Iokath