A rare 17th century brass astrolabe, a hand-held astronomical supercomputer, from Maharani Gayatri Devi of Jaipur’s collection is set to fetch millions at a Sotheby’s auction in London next week.The astrolabe, which forms the centrepiece of the auction house’s ‘Arts of the Islamic World and India’ sale on Wednesday, went on display this weekend and is estimated to fetch between 1.5 and 2.5 million pounds. Dating back to 1612, it is believed to be the largest of its kind and was created by two brothers for a powerful Mughal nobleman in Lahore.The intricate device was part of the royal collection of Maharaja Sawai Man Singh II and by descent his wife Gayatri Devi, Rajmata of Jaipur, before passing on into private collection.“It was commissioned by Aqa Afzal, a really powerful Mughal nobleman who at the time was overseeing the administration of Lahore under Emperor Jahangir, and the object was clearly conceived as something befitting a man of his considerable standing,” the auction notes revealed.“The craftsmanship is quite staggering: 94 cities catalogued inside with their longitudes and latitudes, 38 star pointers connected by floral tracery, five precision-calibrated plates, and degree divisions so fine they are subdivided down to a third of a degree. “The inscription describes it as an ‘asturlab-e tam’, a complete astrolabe referring to the fact that its plates carry a full 90 altitude circles,” it added.The astrolabe is inscribed with the Persian names of the stars and the Sanskrit names in Devanagari script with plates, including the locations for Mecca, Bijapur, Ajmer, Kashmir and Lahore.From a single brass disc, the ancient device could be used to tell the time, map the stars, calculate the position of the sun, find the direction of Mecca and navigate.