# Suryasiddhanta

By Swami Harshananda

## Origin of Surya-siddhānta[edit]

Religous astronomy is a very ancient science. Its source-book is the Surya-siddhānta. It was taught by Surya^{[1]} to Māya^{[2]} at the end of the Kṛtayuga. The work that is available now might have taken shape during A. D. 400. Varāhamihira^{[3]} made use of this work in his Pañcasiddhāntikā. It has three commentaries, the authors being Kamalākara^{[4]} Parameśvara^{[5]} and Raṅganātha.^{[6]} Of these, the last one is the most detailed.

## Content of Surya-siddhānta[edit]

The book is divided into 14 chapters. An oveview of the content of the book can be listed as belows:

- Chapter 1: It deals with the mean motion of the planets. It also gives enough information to calculate the mean daily motion of the planets.
- Chapter 2: The method of calculating the true position of a planet including the corrections needed for its retrograde motion is given here.
- Chapter 3: This chapter deals with direction, place and time. The method of constructing a sun-dial is also given.
- Chapter 4: Both the eclipses, especially the lunar eclipse, are dealt with here.
- Chapter 5: Calculations for the parallax of the solar eclipse are given here.
- Chapter 6: This describes the manner of exhibiting by a projection, the various phases of an eclipse.
- Chapter 7: Planetary conjunctions are the subject dealt with here.
- Chapter 8: This chapter gives the positions of the various nakṣatras or groups of stars.
- Chapter 9: Heliacal rising and setting of the planets are described here.
- Chapter 10: This gives the calculations needed to correctly state the rising and setting of the moon.
- Chapter 11: This is partly astrological in nature. The malignant character of the time as related to the sun and the moon is given here along with the necessary rules for calculating it.
- Chapter 12: The theory of creation of the world is the subject-matter of this section.
- Chapter 13: This deals with certain instruments needed for the determination of time.
- Chapter 14: Different modes of measuring time solar, sidereal, civil or lunar are described here.

## Epilogue[edit]

The text available at present has undergone several corrections over the centuries, the last one being in A. D. 1500. The trigonometric function of sin is found in this work.

## References[edit]

- The Concise Encyclopedia of Hinduism, Swami Harshananda, Ram Krishna Math, Bangalore