Discernment of the Truth of Astronomical Principles

The details of the previously performed actions? regarding the mixture of planetary operations and their results have been illuminated. 30 Thus, in the Siddhanta Shiromani, in the section titled the Chapter on the Sphere original: Goladhyaya; the section of Bhaskara II's work dealing with spherical astronomy and celestial geometry, the principles regarding the observation of the heavens are established for the benefit of scholars. 31

The point of intersection original: sampata; the node or intersection of the celestial equator and the ecliptic where the visible celestial equator meets the path of the sun is fixed at the beginning of Aries original: meshadi; the first point of the zodiacal sign Aries, traditionally the vernal equinox. Similarly, the starting point of the Ashvini original: ashvini; the first of the 27 Nakshatras or lunar mansions constellation is considered fixed and is joined with the position of the Mean Sun original: madhyarka; the sun's position calculated as if it moved at a uniform rate. Through the westward rotation of the heavens, the equinoctial points complete one full rotation in the period of a day and night. Therefore, for all regions on the earth, the rotation of the celestial sphere, being attached to the heavens, is constant. This single rotation is equal to the total minutes of the circle of one's own daily rotation.

However, when one rotation is completed, the Mean Sun has moved slightly forward in its own path. Because of this motion of the Sun, the time taken for the Sun to return to the same position in the sky is slightly longer than one full rotation of the stars. The difference is caused by the minutes of the Sun's daily motion. When the return of the Sun is calculated including these minutes of motion, it is only then that the point of the beginning of Aries, situated above, completes its circuit. The return of the Mean Sun to the meridian occurs after a full rotation plus the time taken to cover its daily displacement. This specific duration, from one sunrise to the next, is accepted by the technical name Savana Day original: savana dina; a civil day, measured from sunrise to sunrise. Thus, by the same force of the Provector Wind original: pravaha-anila; in ancient Indian cosmology, the celestial wind believed to drive the planets and stars westward that carries the stars, the Sun is also moved, but its actual position changes relative to the stars. 32

Because of this, the duration from one sunrise to the next is one Savana Day. Within that period, the celestial sphere actually completes slightly more than one rotation. It must also be understood here that while the Sun moves, the ecliptic itself moves due to the Precession of the Equinoxes original: ayanamsha; the longitudinal difference between the tropical and sidereal zodiacs caused by the earth's axial precession. The calculation of the day must account for this shift. If one considers only the rotation of the celestial circle without the Sun's additional motion, the count of days would be different. This has been stated by the Blessed Sun himself in his own treatise, the Surya Siddhanta original: kha-siddhante; referring to the Surya Siddhanta, one of the most authoritative ancient Sanskrit texts on astronomy, where he defines the days based on the Sun's transit through the equinoctial points. Thus, the rotations are understood through the Sun’s motion. 33

Therefore, a single Savana Day consists of one full rotation of the stars plus the time corresponding to the Sun's daily motion. Every Savana Day represents one rotation of the heavens and the time elapsed as the Sun moves from its previous position. When the daily motion is accounted for, a single revolution of the equinox is completed. In terms of precise time, the number of Savana rotations is slightly different because of this constant shifting of the Sun.