Samrat Yantra
new Historic Calibration work at the Samrat Yantra
Samrat Yantra is an Equinoctial Sundial. One can see its triangular gnomon in the view above - the hypoteneuse of this right angled triangle is parallel to the Earth's axis - so that the hypoteneuse points towards the North Celestial Pole - roughly in the direction of the Pole star.
There are two Quadrants quarters of a circle - placed parallel to the plane of the Earth's Equator, on either side of the gnomon. The shadow of the Sun would be at the top of the western quadrant at the time of Sunrise and go down towards the bottom of the quadrant as the local Solar Noon approaches. Past the local Solar Noon the shadow starts growing on the Eastern Quadrant - reaching its top at Sunset. The position of the shadow along the instrument at different times of the year can be calibrated.