Jantar Mantar

Dhruva Darshak Pattika  

This is the second instrument here which is used to see the location of Pole star (Dhruva Nakshatra) which acts as a compass. Pole star is always on the North side.  

Nadi Valaya Yantra (24 hours sundial) 

This instrument shows 24 hours time with the help of the Sunlight and the Moonlight. There are a pair of circular plates, one facing North and the other facing South. Nadi Valaya  represents the two hemispheres (northern and southern) of the Earth. The wall of the plates is inclined at an angle (gradient), that the instrument is always parallel to the Earth’s equatorial plane. At the centre of the circular plate, you see a rod (needle). There are 24 slabs placed on the circular plate with markings written in Hindi. The shadow of the needle falls on these markings on the dial. The southern hemisphere clock is the winter clock while the northern hemisphere clock is the summer clock which works for six months alternatively.

Yantra Raj  

This is used to calculate Hindu calendar. It is 2.43 metres diameter bronze astrolabe, one of the largest in the world. This is only studied during night by the astronomers and astrologers to find the position of stars and planets. There are markings on the instrument where you can see the degree, position and name of the stars and planets. There is a complete circle (360 degree) marked on the instrument. There are lines depicting the latitude and longitude. There are points on the line depicting North pole and South Pole. There is also a hole at the centre depicting the equator. They have also written the name of the stars in Hindi, for example: Ashwini, Bharani, Krithika Nakshatra etc .

Jai Prakash Yantra  

This instrument is divided into two, part A and part B. There are two hemispherical bowl based sundials with markings on the white marble slabs. These two are complementary to each other. The missing marble in part A can be seen in part B and vice versa. This instrument shows the zodiac sign (sun sign). There are stairs to go under these instruments for two reasons; one to study the accuracy and the other is to clean the instrument for maintenance. There are four wires tied to the sides of the hemispherical bowl and at the centre there is a metal plate. The shadow of the metal plate will fall on the marble which shows the Rashi (Hindu astrology) where the sun is moving. The Zodiac sign will be the same, but it works for 1 hour alternatively, one hour in part A and one hour in part B.  There are also few instruments showing different Zodiac signs which help to write the Kundali seeing the position of the Sun.

Ram Yantra 

With this instrument, we can measure the altitude of the Sun above the horizon as well as the rotation of the Earth.  It consists of two parts: Part A and Part B; the missing stones in part A are found in part B and those missing in part B are seen in part A. There is a pole in the centre of both part A and part B. If the shadow falls on the marble it is said to be working while, if it falls on the missing marble then that part of the instrument is not working and we have to look for the shadow in the other instrument. 1 hour part A works and 1 hour part B works, like the Jaiprakash instrument.  

Palbha Yantra

A circular instrument with a pipe at the centre. The shadow of the pipe falls on the wall showing the angle of the altitude of the sun above the horizon.  As the sun goes up the angle changes and the shadow moves towards 90° at 12 noon. But Jaipur is not on the equator line, it is 27 degrees North latitude, so,  90 degrees minus 27 degrees is equal to 63 degrees. Exact right angle will be formed at 63 degrees at 12 noon. There are latitude lines drawn on the table surface which shows the altitude of the sun. The longitude lines are drawn on the walls which shows the rotation of the sun 24 hours (360 degrees).