Jantar Mantar of Raja Jai Singh Sawai

Introduction to Astronomical Instruments

Ancient Indians developed various astronomical instruments for precise measurements of celestial bodies. These instruments aimed to determine the positions and movements of celestial objects accurately.

Sanku (Gnomon)

The Sanku, also known as a gnomon, is a simple vertical stick with a pointed tip. It is used to establish cardinal directions, which is crucial for any astronomical observation.

To use the Sanku, place it vertically on level ground, ensuring its tip points to the zenith. Draw a circle around the base and mark the points where the gnomon's shadow touches the circle in the forenoon and afternoon. These points indicate the east-west line, as shadows of equal length are symmetrical with respect to the north-south line.

Nadivalaya

The Nadivalaya is a large wooden circular disc with an axis at its center. It is divided into 60 ghatikas and 12 zodiac signs. The disc is rotated until the axis's shadow aligns with the Sun's position at sunrise. The number of ghatikas between the sunrise point and the shadow's position indicates the lagna (ascendant).

Cakra-Yantra

The Cakra-Yantra is a metal or wooden plate with a needle at its center. When sunlight falls on both sides, the needle's shadow indicates the Sun's angular height. Raja Sawai Jai Singh built large Cakra-Yantras in Jaipur and Varanasi, mounted on pillars and fixed to revolve around an axis parallel to the Earth's axis.

Jantar Mantar Observatories

Raja Sawai Jai Singh (1686-1743 CE) recognized the limitations of European instruments and sought to build large, sturdy instruments resistant to wear, tear, and weather. He constructed Jantar Mantar observatories in Delhi, Jaipur, Varanasi, Ujjain, and Mathura, housing a collection of massive astronomical instruments. These observatories, particularly those in Delhi and Jaipur, showcase the astronomical knowledge and engineering prowess of the time.

Conclusion

The astronomical instruments discussed in this document, along with the Jantar Mantar observatories, highlight the rich tradition of astronomical observation and innovation in India. These instruments and observatories served as tools for precise measurements and calculations, advancing the understanding of the cosmos.