Sasthamsa PDF Print E-mail
Written by Yogesh Soman   
Sunday, 26 March 2006 00:41

A Sasthamsa yantra is a 60 deg arc built in the plane of meridian within a dark chamber. The instrument is used for measuring the declination, zenith distance, and the diameter of the sun. Figure explains the principle of its operation. The figure represents a dark chamber with a 60-degree arc facing south. The arc is divided into degrees and minutes. High above the arc, at its center on the south wall, is a pinhole to let the sunlight in. As the sun drifts across the meridian at noon, its pinhole image falling on the Sasthamsa scale below enables the observer to measure the zenith distance, declination, and the diameter of the sun. The image formed by the pinhole on the scale below is usually quite sharp, such that at times even sunspots may be seen on it.

It has its origin in the Islamic tradition of astronomy. According to Kennedy, the instrument was invented by Abu Mahmud al-Khujandi in the late 10th century.

The principle of Sasthamsa Yantra. The instrument displays a pin hole image of the Sun over a 60 degree meridian scale. The image of the Sun is highly exagerated in above fig.


Last Updated on Sunday, 26 March 2006 00:48