In my opinion, Astangata Harana is applied only when a Graha is Asta. A Graha is Asta when it is within the orb of combusion. We can say that angular displacement between the Graha and Surya is 0, then full Harana of 1/2 is applied. Harana is zero when the displacement is more or equal to the orb of the Graha. In this case, we do not see the position of the Graha in various houses from Surya. What matters is how close the Graha is placed from Surya and the closeness should be within the orb.