Astronomical instrument of Water clock is the process with which water is locked in a vessel and then released to calculate the time taken for its discharge. The time which is taken for complete discharge of the water shall estimate the time of the day. This process was initially introduced in Vedanga Jyotisa and was also used in Siddhanta Jyotisa.
Chakra or Circle
The Chakra is the second instrument which is introduced in Hindu astronomy in which a circle is introduced. It is divided into 360 degrees each provided with an axis at the centre perpendicular to its plane and suspended with a string. The circle is used to measure the Zenith distances and the longitude which has been later on used by the future generation scholars including Brahmagupta and Lalla till Bhaskara II who describes it as a versatile yantra.
Capu, Dhanu, Kartari, Turiya
These are the instruments which are used from time to time. While Capu is a half circle, Dajhanu is an arc, Kartari is also a type of arc instrument and Turiya is a quadrant. The first instrument was mentioned by Bhaskara II while the second was introduced by Brahmagupta, the third mentioned by the astronomers of the future times, the fourth one can find its description in the Rig Veda which was used to calculate the eclipse.
Armillary Sphere or Gola Yantra
This is a wooden model of celestial sphere which shows various circles used in Astronomy. The Gola Yantra was mainly introduced for the purpose of demonstration. The outer sphere had a polar axis which represented the horizon, meridian, equinoctial, the prime vertical, etc. This also calculates the position of the stars and their location in the space which shall include both the solar as well as the lunar methods of calculating the cosmos. These have references in Surya-Siddhantya, as well as Siddhanta Shiromany.
Astronomical Instruments used by Maharaja Sawai Jai Singh
Hindu astronomy received a lot of encouragement from the Maharaja Sawai Jai Singh of Jaipur who introduced new lot of instruments to calculate the movement of stars, planet, and their effect on time and other social life. Jai Singh used both metal instruments as well as the masonry instruments which made no distinction between the instruments used by the Muslims or the Hindus. He established an astrological lab called the astrolabe which is taken from the traditions of Central Asia and the Muslim countries which was further used by the Arabs as well as the Persians.
Masonry Instruments were constructed in Jaipur under special supervision of the Maharaja who aimed to equip the people of Jaipur as well as Delhi to be vigilant about the accuracy of time. These are mainly made up of geometrical measurements which are based on pure mathematics and geometry of Ancient Indian Tradition. These instruments included the Sun Dial and those instruments which could calculate the position of the equator and the sun accurately. The other instruments include the digammas and the circular protractor.
Thus, the astronomical instruments had been one such vital contributions of the age on which the entire nation depended for its social and political administration. Hindu Astronomy continues to hold its value for these instruments which are exhibited in the Jantar Mantar of Delhi as well as Jaipur.