NSA member and regular presenter Mark Christensen enlightens us with "The Jantar Mantar: The Biggest Calculating Instrument in the World". The Jantar Mantar is a World Heritage site in Jaipur, India, consisting of 19 different sundials. Its builder, Rajput King Jai Singh, was an astrologer in the 1700s and observed that astronomical positions in the tables then in use did not correspond to reality. So he directed the construction over almost 40 years of a series of more accurate instruments. Recent photographs of the restored site will be exhibited, along with examples of the types of measurements made and details about its history.