From ( Pos_Lord ), count forward ( D ) houses. That house number is the preliminary Arudha Lagna (( AL_pre )).
Exception: AL_pre == Lagna (1) → final AL = 10th house. arudha lagna calculator
Let ( D = Pos_Lord \to H_L ) (forward count in zodiac order, not retrograde). ( D = (H_L - Pos_Lord) \mod 12 ); if result = 0, set ( D = 12 ). From ( Pos_Lord ), count forward ( D ) houses
# 5. Apply exceptions if al_pre == 1: # Lagna itself al_final = 10 elif al_pre == 7: # 7th from Lagna al_final = 4 else: al_final = al_pre From ( Pos_Lord )
# 4. Preliminary AL al_pre = (lord_house + delta - 1) mod 12 + 1