In a paper published in 1957, American astronomer Olin Chaddock Wilson and Bappu had described what would later be known as the Wilson-Bappu effect. The effect as described by L.V. Kuhi is: 'The width of the Ca II emission in normal, nonvariable, G, K, and M stars is correlated with the visual absolute magnitude in the sense that the brighter the star the wider the emission.' The paper opened up the field of stellar chromospheres for research.
On his return to India, Bappu was appointed to head a team of astronomers to build an observatory at Nainital. His efforts of building an indigenous large optical telescope and a research observatory led to the founding of an optical observatory of Kavalur, inaugurated in 1986 by Rajiv Gandhi, who named the observatory, and its large telescope after Bappu. The Vainu Bappu Observatory is one of the main observatories of the Indian Institute of Astrophysics, also initiated in its modern avatar by Bappu in 1971. Later, a number of discoveries were made from the Vainu Bappu Observatory.
^At Kavalur the first observations with an indigenously built 38 cm telescope were made in late 1967. In Kavalur the one-metre Zeiss telescope was installed in 1972, and the very next month, during an occultation event, scientists discovered a trace of atmosphere on Gynymede, the largest satellite of Jupiter. Five years later the same telescope discovered the rings of Uranus. -- Indian Astronomy : From Jantar-Mantar to Kavalur, Department of Science and Technology, Government of India.