* Astronomy

Between 1727 and 1734 Maharajah Jai Singh II of Jaipur constructed an astronomical observatory, in Jairpur, the capital of the federal state Rhajasthan in west central India. The observatory, or "Jantar Mantars" as they are commonly known, incorporate multiple buildings of unique form, each with a specialised function for astronomical measurement.

Located about 250 meters south of Connaught Place, Jantar Mantar, (Sanskrit; translated as “Magical Device”), the pale pink ancient observatory will become "useful" again. Introducing amateur astronomers to its finer points this Tuesday, the Nehru Planetarium has organised a lecture tour at the monument to show young enthusiasts the Spring Equinox.

A chance to understand the Spring Equinox in not just textbook term, the lecture will give them an idea about the mathematics behind this phenomenon. Giving students the idea of the "zero" angle, the lecture tour has been organised in collaboration with the Archaeological Survey of India, the Amateur Astronomers Association and Apeejay Park Group of Hotels.
Not the first time that the Nehru Planetarium has decided to use Jantar Mantar to explain the mystic working of the sun, this is an attempt to bring alive the historic observatory where each "yantra" is built to measure the movement of the sun.



Apart from introducing young children to science, such lectures also give students an opportunity to learn more about historical monuments. Making them realise the genius of observatories like Jantar Mantar that were built before the advent of modern technology, the idea is to get them to understand how these huge strangely shaped buildings work.
These lecture tours have got students familiar with instruments like "Misra Yantra'' -- that can be used to calculate the angle of the sun from the equator, also known as the declination.
Measured through the marble circles carefully engraved with angular divisions, known as the Niyat Chakra, this instrument is used to measure the declination of the sun. And the lecture tour on Tuesday will give students and enthusiasts a chance to "see" the movement in all its glory.


Position: 28°37'35.76"N. Longitude: 77°13'0.07"E.
Height above sea level: 212 metres

The Jantar Mantar Observatory contains six instruments. The most important or the 'Supreme Instrument' in Jantar Mantar is the Samrat-Yantra, the huge sundial. It is an 'equinoctial dial' or 'equal hour' sundial, consisting of a triangular gnomon with the hypotenuse parallel to the earth's axis. On the either side of the gnomon is a quadrant of a circle parallel to the plane of the equator.

South of this is the Jai Prakash yantra, an instrument which consists of two concave hemispherical structures, used to ascertain the position of the Sun and other heavenly bodies. Jai Singh himself designed this instrument and hence the name, which means 'Invention of Jai'. The Ram-Yantra is south of the Jai Prakash and was used for reading azimuth (horizontal) and altitude (vertical) angles. It consists of two circular buildings with a pillar at its centre.

Northwest of this is Misra Yantra, which combines five instruments in one and hence its name. It looks like a stylised 'namaste', the Indian form of greeting, folded hands and palms pressed together. The Niyta-Chakra indicates the meridians of Greenwich, Zurich, Notkey (Japan), and Serichew (Pacific Ocean).

Dakshinottarabhitti-Yantra was used for obtaining meridian altitudes and Karka-rasi-valaya indicated the entry of the Sun in the constellation Cancer. The Agra Yantra (or amplitude instrument) is the second quadrant on the west side of the building and the exact purpose of this structure is not definitely known.
The Samrat Yantra, based on the same principles as the large Samrat Yantra, was used to give time and declination before and after noon. Built with brick rubble and plastered with lime, similar observatories were also made at Jaipur, Ujjain, Varanasi and Mathura.

To the east of these instruments, there is a Temple of Lord Bhairava, which was also probably built by Maharaja Jai Singh. The observatory is maintained by the Archaeological Survey of India and is a protected monument under the ASI Act. The gardens that surround the instruments have seasonal flowers and lawns, where visitors can sit.

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