Jantar Mantar Ujjain

By Sanjeev Nayyar [email protected] | 2007

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Ujjain enjoyed a position of considerable importance in the field of astronomy. According to Indian astronomers, the Tropic of Cancer is supposed to pass through Ujjain. It is also the fist meridian of longitude of the Hindu geographers. The observatory extant today was built by Raja Jai Singh (1686-1743). Of the many observatories built by him at Jaipur, Delhi, Varanasi, Mathura, and Ujjain, the one at Ujjain is still in use actively. Motions & pictures are studied through these instruments. On this count people call it Yantra Mahal too. This observatory was renovated by Madhav Rao Scindia, the then ruler of Gwalior state in 1923. What you see is my Guide. Read Travelogue.

Transit Instrument: this instrument is built in the plane of the meridian circle (the circle joining north, south and zenith point). It is used for observing the zenith distance of any celestial body (corresponding to its mid-day). There are two pegs at the top of the instrument fixed with string in the center of graduated quadrants. When the object is in the south of the prime vertical (the circle joining east, west and zenith point), the southern peg is to be used, otherwise the northern peg is to be used. At the time of the transit of the celestial body, the observer has to keep his eye on the string and move it forward or backward to determine the particular position of the string at which the center of the heavenly body could be seen, through the point of intersection of peg and wall. The reading of the quadrant at the position of the string gives the zenith distance. After 12.26 no use since Sun crosses the instrument.

Nadi Valay Yantra: This instrument is built up in the plane of the celestial equator. It has two parts northern & southern. When the sun is in the northern hemisphere for six months, the northern disc is illuminated. When the Sun is in the southern hemisphere for the next 6 months the southern side is illuminated. A peg parallel to the axis of the earth is fixed in the center of the disc. The shadow of the peg gives the apparent time at Ujjain. This instrument is used to decide if a celestial body is in the northern or southern hemisphere. Keeping the eye at any suitable point on one of the disc, observe the celestial body. The object is then in the northern or the southern hemisphere according as it is visible from the north or south disc.

Samrat Yantra.

Digansha Yantra: This instrument is used to find out the Altitude (distance from the horizon and the (angular distance from the Earth or western point along the horizon) of any celestial body.

For this purpose a device called Turiya Yantra is fitted on the pole which stands on the circular platform. Arrange the position of the Turiya Yantra in such a way that the two holes of the Turiya Yantra are in line joining the celestial body such that it may be visible through both the holes. The suspended thread of the turiya yantra gives the altitude on the graduated scale of the quadrant. Distance of sun and moon can be calculated from here. Can know at what degree is sun at any point during the day. Used to know 8 types of clouds, some indicated heavy rain others light rain although this is for Ujjain area only.

Shanku Yantra: At the center of the plateform a vertical shanku is fixed. The platform is in horizontal plane. 7 lines are drawn from it with help of the shadow of the . The 22nd December represents the shortest day of the year, on 21st March and 23rd September the days & nights are equal and 22nd June is the longest day of the year. These lines also represent the zodiac signs. With the help of the shadow of the G the angle of elevation and zenith distance of the sun can be determined. On equinoctial days the mid day shadow of the G represents the latitude of Ujjain.

Sun-dial: the upper planes of the two walls on the sides of the steps in the middle of this instrument are parallel to the axis of the earth. Hence the pole star is visible at night in the direction of these planes. To the east and west of the wall are two quadrants, which are in the plane of the celestial equation. Has minutes and fractions of a minute are engraved on the quadrants. When the sun in the sky the point at which the shadow of the edge of the wall falls, gives directly the local time of Ujjain. The correction in minutes engraved on the stone slab to the east and west of the instrument when added to this apparent time will give Indian standard time. This instrument is mainly used to find out the declination of any celestial body ie its distance from the celestial equator towards north or south. First find out the particular point on the edge of the quadrant from where the center of the celestial body could be observed to coincide with the edge of the wall. The reading at this point of the wall gives the declination.

Sundial Time that you can see on the bottom right of the previous picture.