Jantar Mantar, the observatory, built by Sawai Jai Singh II where it holds a collection of about 19 astronomical instruments. The heritage site magnifies the world’s largest stone dial. It has been recognized by UNESCO. The Rajput king built the observatory in 1724. It was constructed for naked-eye observations of the celestial bodies. it is also used to measure time. It also follows three classical celestial coordinates to track the positions of heavenly bodies- namely the horizon-zenith local system, the equatorial system, and the ecliptic system.

The main aim of Jai Singh II was to refine the ancient Islamic zij tables, to measure the exact hour continuously, and to define the calendar in a more precise manner. Therefore this observatory is an example of the Ptolemaic positional astronomy which was an example to many civilizations. The site was the heart of the royal capital during the late Mughal period of India. The king has built three more observatories in various places. In addition, the Jaipur observatory is the largest as well as more accurate than others.

Jantar Mantar is one of the other five observatories which are built in New Delhi, Ujjain, Mathura, and Varanasi. Whereas the heritage site in Jaipur is located near City Palace and Hawa Mahal. The instruments at the 5 Jantar Mantar, all work on the principles of spherical trigonometry.

Origin of Jantar Mantar

The name Jantar is derived from yantra a Sanskrit word, meaning “instrument, machine”, and mantar from mantrana also a Sanskrit word “consult, calculate”. Therefore, Jantar Mantar literally means ‘calculating instrument’. Among all other observatories, this is the largest that is well preserved. Also, it has a collection of 19 architectural astronomical instruments.

Materials of Jantar Mantar

It is built from local stone and marble, each instrument has an astronomical scale. In general, it is marked on the marble inner lining. Also, bronze tablets, bricks, and mortar are used in the building. Therefore, the instruments in the monument spread over about 18,700 square meters. But, the king decided to build the astronomical instruments with stone and marble due to the long life of this building material. Moreover, in all ways, the materials were better than metal where it has resistance to wear and tear easily. The instruments allow the visitors to observe the astronomical positions with the naked eye. Also, some of the instruments are built from bronze.

Present day at Jantar Mantar

The observatory was under active use until 1800 various amount of restoration has happened even in the 19^th century. There were some important restorations that had taken place during the end of the nineteenth century which a new life to the observatory. The masonry instruments were restored recently in 2006. They have also preserved some of the original materials. However, today the site is open to tourism where they are showing users how to read time through these impressive instruments. Moreover, Jantar Mantar is now protected as the National Monument of Rajasthan (1968). Similarly, the site of 1.8652 ha (4.609 acres) is an applicant for the World Heritage List, campaign 2010.

These are some of the instruments used at the observatory of Jantar Mantar at Jaipur, Rajasthan.

Vrihat Samrat Yantra

• Sundial
• Triangular wall
• 22.6 meter high and largest quadrants of radius 15.5 meter
• Placed in the north-south direction
• Recordings movement of the sun to read time
• Indian Standard Time = Local
• Time ± Equation of Time ± Longitude difference.

Small Samrat Yantra at Jantar Mantar

• Time accuracy of 20 seconds
• Local time according to the eastern and western side quadrants
• The shadow of the triangular wall moves equal distances in equal time intervals on the quadrants.

Unnatamsa Yantra

• An instrument for measuring altitude the angular height of an object in the sky.
• The use of this instrument is to find the declination and distance from the ecliptic and equinox of the sun and stars.
• It is a metal ring that divides into four segments by vertical and horizontal lines and it also has a hole in the middle.
• The position and orientation of the instrument allow measurement of the altitude of celestial bodies.

Rashi Valaya Yantra at Jantar Mantar

To measure the celestial latitude and longitude of the celestial bodies.

Jai Prakash Yantra

• Representation of half celestial sphere rim represents horizon for finding all the positions of the heavenly bodies.
• It consists of marble slabs with an inverted image of the sky.
• This instrument allows the users to move inside it with the given large scale for accuracy.
• Therefore, It also measures the altitudes, azimuths, hour angles, as well as declinations.

Nadi Valaya Yantra at Jantar Mantar

• two circular plates
• placed in a north-south direction
• The wall of the plates, inclined towards the south at such an angle that the instrument.
• It remains parallel to the plane of the Earth’s equator.
• The instrument consists of two sundials on different faces.

Chakra Yantra

A ring instrument which measures the global co-ordinates of declination and the hour angle of a celestial object.

Digamsha Yantra at Jantar Mantar

• The instrument is also known as azimuth
• The instrument has a pillar in the middle of two concentric outer circles.
• method of determining the azimuth of a celestial object.

Rama Yantra

To measure the local co-ordinates of altitude and azimuth of a celestial object.

Kranti Vritta Yantra at Jantar Mantar

• The use of this instrument is to find the declination and distance from the ecliptic and equinox of the sun and stars.
• Also, The instrument also measures the longitude and latitude of the celestial bodies.

Yantra Raj Yantra

• An adaptation of an astrolabe a medieval instrument for the measurement of time and the positions of celestial objects.
• It is A 24-meter bronze astrobale and one of the largest in the world.
• therefore used only once a year to calculate the Hindu calendar.

Dakshin Bhitti Yantra

It measures the meridian, altitude and the zenith distances of celestial bodies.

Dhruva Darshak Pattika

Used to observe and find the location of pole star with respect to other celestial bodies.

Shastansh Yantra

• It is located next to the Vrihat Samrat Yantra.
• The instrument has a 60-degree arc built in the meridian plane within a dark chamber.
• During the afternoon, the sun’s image falls on the scale enables the observer to measure
• calculate the zenith distance, declination, and also diameter of the Sun.

Kapali Yantra at Jantar Mantar

• This instrument measures the coordinates of celestial bodies in azimuth and equatorial systems.

Misra Yantra

This is a mixed instrument which has a compilation of five different instruments.

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