Rasi is a house of the sun or zodiac sign in the way that a Nakshatra is a house of the moon. A Rasi is 30 degrees. Divided into 9 navamsas, each amsa is 3 degrees and 20 mintes. Hence, the division of the moon into padas and the sun into amsas reesults in their becoming divided into equal sections of 3 degrees, 20 miinutes.