The Jantar Mantar of New Delhi

The Jantar Mantar in New Delhi, India, is an astronomical observatory constructed in 1724 by Maharaja Jai Singh II. It consists of 13 architectural astronomy instruments erected to compile astronomical tables and predict the movement of the sun, moon, and planets. However, during my visit in November 2016 the smog in Delhi was so dense that even the sun was barely visible and the instruments were therefore useless.