Astronomical instruments (Yantras) in Indian Astronomy

A Gift of Astronomical Instruments

In 1875-76, during his tour of India, the Prince of Wales received a set of astronomical instruments as a gift from the Maharaja of Banaras. These instruments were crafted based on descriptions in the Siddhanta Shiromani, a text written by Bhaskaracharya in 1150 CE. The gift included:

• Digamsa-Yantra: Measures the azimuth of celestial bodies.
• Dhruva-Protha-Chakra-Yantra: Measures the declination of celestial bodies.
• Yantra-Samrat: Determines the distance from the meridian and the declination of celestial bodies.
• Bhitti-Yantra: A mural quadrant.
• Visuvad-Yantra: Ascertains the time difference of a celestial body from the meridian.
• Palaka-Yantra, Chakra-Yantra, Chapa-Yantra, Turiya-Yantra: Measure zenith distance and altitude of the Sun.
• Sanku (Gnomon): Ascertains directions, observer's location, latitude, and time.
• Armillary Sphere: Represents celestial circles and helps determine spherical triangles.

The Maharaja also presented a clock displaying zodiac signs, moon phases, dates, weekdays, hours, and minutes. These instruments and the clock highlight the significance of astronomy in India.

Importance of Astronomical Instruments

Astronomy relies on observation and computation, requiring accurate measurements of celestial bodies' positions and movements. Visual observations alone are not always accurate, necessitating instruments for precise measurements and timekeeping.

Astronomical Instruments in Siddhanta Shiromani

The Siddhanta Shiromani describes various astronomical instruments (yantras), including:

• Gola-yantra (Armillary Sphere): Represents movable and fixed celestial circles, serving as an astrolabe.
• Cakra-yantra: A wheel-like structure used to determine longitudes and latitudes of planets.
• Capa-yantra and Turiya-yantra: Half and one-quadrant versions of the Cakra-yantra, respectively.
• Nadivalaya: A chakra in the equatorial plane used to determine timings of rising and setting of signs.
• Ghati-yantra: A water clock for timekeeping.
• Nara/Sanku (Gnomon): Made of ivory or metal, used for various measurements.
• Phalaka-yantra: A plank with a graduated circle for measuring zenith distance.
• Dhi-yantra: A stick instrument with a plumbline for determining heights and distances of objects.

These yantras are crucial for observation, calculation, and prediction in astronomy.

This discussion provides a glimpse into the rich tradition of astronomical instruments in India, as documented in the Siddhanta Shiromani and exemplified by the gift to the Prince of Wales.