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. This rare historic nod to astronomy lands on the auction circuit soon after the recent Artemis II space mission.

These astrolabes are works of artistry as much as instruments of science and many now describe them as olden day smartphones, Sotheby's reflected.

According to the official literature referenced, Lahore in the early 17th century was the epicentre of astrolabe-making in the Mughal world. Known as the "Lahore School", the craft was kept within a single family and passed down from father to son across four generations.

The two brothers who made this particular instrument, Qa'im Muhammad and Muhammad Muqim, were among the most celebrated makers the school ever produced. Between them they made a number of astrolabes that survive, but they only ever worked together on two and the one on display in London now is one of them.

The only other astrolabe they collaborated on, now in the National Museum of Iraq, has a diameter of just 12 centimeters. The one coming up for the auction next week is at a different scale, at 29.5 cm diameter and nearly 50 cm in height.

Other key highlights of the auction include a Mughal painting of Jahangir estimated to fetch between 150,000 and 200,000 pounds and 19th century paintings from India expected to go under the hammer for around 80,000 pounds.