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The Digamsa is a cylindrical instrument that has a simple method of determining the azimuth of a celestial object. Digamsa or the azimuth of a celestial object is the relative angular position of the object measured eastwards,starting from the direction North.

The instrument consists of a small knob (gnomon) placed in the centre of three co-axial cylinders. To determine the azimuth of a celestial object at night, an ordinary string is needed to be attached to the central knob. The other end of the string is suspended over one of the outer cylinders, using conventional weights. The circular rim of the cylinders is marked into 360 degrees and further subdivisions to indicate the azimuth.

The string is moved over the rim of either of the outer cylinders and aligned to sight the celestial object. By this process, a vertical plane is defined that contains the object and a point on the horizon. The azimuth can be read from the marking scale on the rim of the cylinder where the string is resting.

Likewise, to measure the azimuth of the Sun, crosswires are stretched on the outer cylinder in East-West and North—South direction. Shadow of the centre of crosswires on the circular scale tells the azimuth.