Treatise on the Sun

49. From the desired ghatikas units of time equal to 24 minutes and asus breaths; the time taken for one respiration, 1/6th of a vinadi, one should subtract the rising time of the portion of the zodiac sign yet to be traversed. From the remainder, the rising times of the subsequent signs should be subtracted in order. 50.

The remainder is then multiplied by thirty and divided by the rising time of the sign this refers to the duration of the rising of that specific zodiac sign at a given latitude. The resulting degrees and minutes are added to the signs already passed; thus, one finds the ascendant lagna; the point of the zodiac rising on the eastern horizon at the horizon kṣitija for that time. 51.

Using the time before or after noon, and the rising times of the signs adjusted for the Sun's position, the meridian ascendant madhya-lagna; the point of the zodiac currently crossing the observer's meridian should be calculated as positive or negative accordingly. 52.

Subtract the rising time of the portion of the sign already traversed from the ascendant, or add the portion yet to be traversed if it is greater; by calculating the difference between the ascendant and the Sun's position in rising time, the calculation of time kāla-sādhana is achieved. 53.

When the Sun is less than the ascendant, it is the remainder of the night; when the Sun is greater, it is day. If the Sun, increased by half the zodiac 180 degrees, is greater than the ascendant, then it is after sunset. 54.

Thus ends the Third Chapter, titled the Chapter on the Three Inquiries Triprasnadhyaya, in the Great Surya Siddhanta original: "Śrī-Sūrya-Siddhānta"; the Sun's Treatise, one of the most significant historical texts of Indian astronomy. 3.

The diameter of the Sun Vivasvat is eight plus six thousand yojanas 6,500; a traditional unit of distance. For the Moon Indu, the diameter is four hundred and eighty yojanas. 480. 1.

These diameters, multiplied by their own specific true motion and divided by the mean motion, result in the true diameters. 2.

The Sun's own revolutions multiplied by the Moon's revolutions and divided by... 2. The Moon's orbit kakṣā is 324,000. When multiplied or divided by the orbit... therefore 5 43,310,500. The diameter of the Moon's orbit divided by fifteen gives the measure in minutes of arc liptikā. 3.

The true motion of the Moon divided by 60 and multiplied by the mean motion... 79 7 5. The result is the diameter of the Earth's shadow, which is the difference between the true solar distance and the Earth's diameter. 4.

The mean diameter of the Moon (480) multiplied by the mean diameter of the Sun (6500) and divided... subtract the result to find the diameter of the darkness the Earth's shadow cone as before. 5.

The Earth's shadow is always six signs 180 degrees away from the Sun. When the Moon's node is at or near that position, a lunar eclipse occurs, depending on the degrees of latitude. 6.

When the signs and degrees are equal, it is the end of the new moon day amāvāsyā. The word "ka" refers to the Sun and "tavācī" refers to the Moon. 1. The difference between the diameters of the two disks... divided by the Moon's diameter = 2.