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The Ram Yantra can measure the local co-ordinates of Altitude and Azimuth, of a celestial object.

The angular height of an object, from the Horizon, is the Altitude. The Azimuth is the relative anglular position of the object measured eastwards, starting from the direction, North.

Each of the cylindrical Ram Yantra consists of a circular wall, floor sectors and a gnomon at the center. The gaps inside the instrument are for facilitating the movement of observers to read the markings and hence, the complimentary instrument is designed in such a way that, the shadow falls on a sector of one of the instruments, if it falls in the gap for the other instrument. Spliced together, the two instruments make a whole cylinder whose inner walls and the floor is a complete reflection of the sky above.

The complete circumference of the Ram Yantra Cylinder encloses 360 degrees of Azimuth. This is then divided into different segments of Azimuth, in the wall and floor sectors of the instrument. The 12 wall and floor sectors inside the two cylindrical instruments, are of unequal width. The East Ram Yantra has 12 degree wide sectors separated by 18 degree wide gaps, while the West Ram Yantra has 18 degree wide sectors separated by 12 degree wide open sections.

The height of the walls and the gnomon has been designed to be exactly equal to the inside radius of the cylinder measured from the outer circumference of the gnomon. Azimuth angles are marked on the floor and walls of the Ram Yantra as sectors. The circular ring near the (non-existent) roof of the building has markings for the Azimuth. The smallest division is one fifth of a degree. Azimuth is zero towards the North and increases eastwards.

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Page last modified on June 25, 2008, at 04:21 AM EST