Treatise on the Sun

The radius-sine multiplied by the sine of declination and divided by the day-diameter gives the asavaḥ original: "asavaḥ"; a unit of time equal to 4 seconds, the time taken for one breath of the earth-sine 61. The arc of this value is added to or subtracted from the quadrant of a circle to determine the length of the day and night 62. In the case of southern declination, the process is reversed; when multiplied by two, these values provide the decrease or increase of the day 63.

The measure of a lunar mansion original: "bhabhoga"; one of the 27 nakshatras is 800 minutes of arc. Similarly, the measure of a Yoga an astrological period based on the combined longitudes of the Sun and Moon is 720 original: "khāśviśaila"; numerical code for 720 or 800 minutes. By dividing the daily motion of the planets by these values, one determines the current Nakshatra, Yoga, and the time elapsed 64.

The Yogas are found by taking the sum of the minutes of the Sun and Moon and dividing by the measure of a Yoga. The remaining minutes, when divided by the sum of their daily motions, provide the time passed in nadis original: "nāḍyaḥ"; a unit of time equal to 24 minutes 65. To find the Tithi a lunar day, representing a 12-degree separation between the Sun and Moon, take the minutes of the Moon minus those of the Sun, and divide by the measure of a Tithi (720 minutes). The remaining time is calculated by the difference in their daily motions 66.

The four fixed Karanas original: "karaṇa"; half of a lunar day are:
1. Shakuni
2. Chatushpada
3. Naga
4. Kimstughna
These occur in order starting from the second half of the fourteenth day of the dark fortnight 67. Then, the seven movable Karanas, starting with Bava, cycle through the month eight times each 68. One should assign half the duration of a Tithi to each Karana. This completes the explanation of the "True Motion" (the calculated movement) of the Sun and other planets 69.

The calculation for the movable Karanas (Bava, etc.) is performed by taking the separation of the Sun and Moon and dividing by seven; the remainder indicates the current Karana. The duration of these is calculated in time units similar to the Tithis 70.

Thus ends the Second Chapter of the Great Surya Siddhanta, titled "The True Motion of the Planets."

Chapter Three: On Direction, Place, and Time

On a stone surface that has been made perfectly level and polished with vajralepa a durable astronomical cement or "adamantine paste", or on a level wooden floor, one should draw a circle with a radius of a desired number of digits 1. In the center of that circle, one should place a gnomon original: "śanku"; a vertical rod used to measure the sun's shadow of twelve digits in height. Where the tip of the shadow touches the circumference of the circle in the forenoon and the afternoon 2, one should mark those two points, designated as the "west" and "east" points...