Narivalaya Yantra

Jantar Mantar Observatory

This is an equitorial sundial of a different design from the Laghu Samrat Yantra, but performing the same function - it measures the local solar time at the latitude of Jaipur. There are actually two paired instruments, one for use in winter (when the sun is in the southern hemisphere) and the other for use in summer, when the sun is in the northern hemisphere. The winter dial is shown in this photo, which was taken in November.

The instrument consists of a thin, rod-like gnomon fixed perpendicular to the masonry dial. The dial is set in the plane of the equator, and the gnomon points to the south pole (for the winter instrument) or the north pole (for the summer instrument). Local solar time is read off from the angular position of the gnomon's shadow on the dial.

You may be able to see from the faint shadow of the gnomon (barely visible in this photograph) that the local time is about 11:00. At noon the shadow points straight down, and here the shadow is about one hour to the left (west) of that. Since the shadow is in the west, the sun is in the east, about one hour before noon.