The several stellar discoveries of the 40-inch telescope at the Vainu Bappu Observatory in Kavalur, Tamil Nadu, were highlighted at the celebration of its 50 years of operation on 15-16 December.

The telescope set up by Professor Vainu Bappu has played a significant role in astronomy with major discoveries like the presence of rings around the planet Uranus, a new satellite of Uranus, the presence of an atmosphere around Ganymede which is a satellite of Jupiter. Other important research conducted with this telescope includes the discovery and study of many 'Be stars',  Lithium depletion in giant stars, optical variability in Blazars, the dynamics of the famous supernova SN 1987A and so on.

The telescope in the observatory under the Indian Institute of Astrophysics (IIA), an institute of the Department of Science and Technology (DST), continues to be relevant because of the backend instruments that engineers and astronomers built over the last 50 years to keep the telescope competitive among its peers. Starting from the Cassegrain photometer and Echelle spectrograph in 1976, the new grating spectrograph in 1978, the fast-chopping polarimeter in 1988 with its replacement in 2016, and the latest NIR photometer in 2021, the observatory has constantly been upgrading its facilities.

“This telescope stands witness to the technology changes in astronomical observations, from photographic plates to modern CCDs,” said Prof. Annapurni Subramaniam, Director IIA. “I am confident that the facility continues to be productive and be used by scientists for years to come,” she added

By the 1960s, it was clear that India needed a high-quality optical observatory to conduct research in modern astronomy, and after an extensive search, Professor Vainu Bappu chose Kavalur as the site for such an observatory. The skies above Kavalur were excellent, and its southern location would allow it to see most of the northern and southern skies. A few years after the observatory started operation, Prof. Bappu placed an order for a 40-inch telescope with Carl Zeiss of Jena (then East Germany), which was subsequently installed in 1972.

The telescope, whose mirror has a diameter of 40 inches (or 102 cm), was installed in 1972 and started producing important astronomical discoveries soon after. More than a generation of astronomers were trained at this telescope as well. The expertise gained by the engineers also enabled IIA to build the fully indigenous 90-inch (2.34 metre) telescope in the 1980s.

To celebrate the golden jubilee of this extraordinary telescope, IIA organised a 1-day meeting on 15 December at its Bengaluru campus, followed by a function at Kavalur on the 16^th. Many of the retired IIA astronomers, engineers, and telescope assistants were invited to the event and were felicitated by the Director IIA. There were a number of talks about important science discoveries from the 40-inch as well as personal reminiscences by the staff from that time. The 7^th issue of “DOOT”, an astronomy magazine published by the students of IIA, was also released at this event.

A contest to paint the 40-inch telescope was organised for students in the primary schools in the villages surrounding Kavalur. The winners were awarded prizes on the 16^th at the observatory during the function.

Participants in the golden jubilee celebrations of the 40-inch telescope, 15 Dec 2022, IIA Campus, Bengaluru

Under the 40-inch telescope with some of the senior astronomers who had used it early in their careers.

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