Chapter 1 Astronomical Adaptive Optics at the Indian Institute of Astrophysics Sridharan Rengaswamy, Ravinder Banyal, Sreekanth Vallapureddy, and Hemanth Pruthvi Abstract Astronomical Adaptive Optics (AO) technology enables real time diffraction-limited imaging and spectroscopy with high sensitivity from ground- based telescopes. It is achieved by using corrective optical elements in the path of the light beam before the final image is formed. The Indian Institute of Astrophysics is deliberating on building new large solar and stellar telescopes, namely the National Large Solar Telescope (NLST) and the National Large Optical Telescope (NLOT) equipped with AO. In view of this, an AO program has been initiated at IIA, with the primary objective of generating expertise in the field of astronomical adaptive optics by developing and demonstrating AO systems in existing small telescopes. In this paper, we start with an overview of astronomical adaptive optics and elaborate on the AO related activities carried out at IIA. 1.1 Introduction Ever since the invention of the telescopes, humanity has been striving to have a clear view of the heavens by building large ground-based telescopes. It was not up until the mid twentieth century astronomers realized that the Earth’s atmospheric turbulence distorts the light, making the image formed by a large telescope to wander randomly, and therefore appear enlarged, at the focal plane. The resultant angular resolution—typically a second of arc in diameter irrespective of the diameter of the telescope—is poorer than the theoretical resolution due to diffraction alone. Mr. Hemanth Pruthvi was affiliated with IIA till April 2019. S. Rengaswamy (B ) · R. Banyal · S. Vallapureddy Indian Institute of Astrophysics, Koramangala II Block,Bangalore, Karnataka 560034, India e-mail: sridharan.r@iiap.res.in R. Banyal e-mail: banyal@iiap.res.in H. Pruthvi Leibniz-Institut für Sonnenphysik, Schöneckstraße 6, Freiburg 79104, Germany © Springer Nature Singapore Pte Ltd. 2020 I. Bhattacharya et al. (eds.), Progress in Optomechatronics, Springer Proceedings in Physics 249, https://doi.org/10.1007/978-981-15-6467-3_1 1