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Browsing by Author "Sridharan, R"

Browsing by Author "Sridharan, R"

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  • Coherent Radio Beacon Experiment (CRABEX) for tomographic imaging of the equatorial ionosphere in the Indian longitudes – Preliminary results 
    Thampi, S. V; Ravindran, S; Devasia, C. V; Sreelatha, P; Pant, T. K; Sridharan, R; Venkata Ratnam, D; Sarma, A. D; Raghava Reddi, C; Jessy Jose; Sastri, J. H (Elsevier, 2007-02)
    To investigate the equatorial ionospheric processes like the equatorial ionization anomaly (EIA), equatorial spread F (ESF) and their inter relationships, a network of ground based stations receiving the 150 and 400 MHz ...
  • Design and modeling of a tunable spatial heterodyne spectrometer for emission line studies 
    Nirmal, K; Sridharan, R; Sriram, S; Murthy, J; Ambily, S; Safonova, M; Sreejith, A. G; Mathew, J; Mayuresh, Sarpotdar (SPIE--The International Society for Optical Engineering, 2018-04)
    Spatial heterodyne spectroscopy (SHS) is an interferometric technique similar to the Fourier transform spectroscopy with heritage from the Michelson interferometer. An imaging detector is used at the output of an SHS to ...
  • Development of image motion compensation system for 1.3m telescope at Vainu Bappu Observatory 
    Sreekanth Reddy, V; Banyal, R. K; Sridharan, R; Aishwarya, S (IOP Publishing, 2020-01-01)
    We developed a tip-tilt system to compensate the turbulence induced image motion for the 1.3 m telescope at Vainu Bappu Observatory, at Kavalur. The instrument is designed to operate at the visible wavelength band (480−700 ...
  • Discovery of an M-type companion to the Herbig Ae Star V1787 Ori 
    Arun, R; Mathew, B; Sridharan, R; Manoj, P; Narang, M; Kartha, S. S; Maheswar, G (Oxford University Press on behalf of the Royal Astronomical Society, 2021-02)
    The intermediate-mass Herbig Ae star V1787 Ori is a member of the L1641 star-forming region in the Orion A molecular cloud. We report the detection of an M-type companion to V1787 Ori at a projected separation of 6.66 arcsec ...
  • Estimation of Fried's Parameter From Specklegrams of Solar Features 
    Sridharan, R; Venkatakrishnan, P; Verma, V. K (Springer, 2002-12)
    A few methods of estimating Fried's parameter (r 0) from specklegrams of solar features are described. Some of these methods were used to estimate r 0 for the speckle data obtained from Kodaikanal Observatory (KO), Uttar ...
  • Image Quality Specification for Solar Telescopes 
    Saraswathi Kalyani, S; Sridharan, R (Springer, 2023-01)
    Modern large ground-based solar telescopes are invariably equipped with adaptive optics systems to enhance the high angular resolution imaging and spectroscopic capabilities in the presence of Earth's atmospheric turbulence. ...
  • Imaging with insolated mirrors 
    Venkatakrishnan, P; Sridharan, R; Gupta, S. K (Astronomical Society of India, 2005-09)
    Modern solar telescope designs are different from the conven- tional concept of vacuum telescopes. These new designs are "open" telescopes which try to minimize the temperature difference between various parts of the ...
  • Measurement of astronomical seeing using long exposure solar images 
    Sridharan, R; Ravindra, B; Prabhu, K (Springer, 2019-01)
    We extend our modified parameter search method (Sridharan, Dashora, and Venkatakrishnan, Solar Phys.222, 35, 2004) of estimating the Fried parameter (r0) from long exposure images to the images obtained from the Hα-telescope ...
  • Measurements of atmospheric turbulence parameters at Vainu Bappu Observatory using short-exposure CCD images 
    Sreekanth Reddy, V; Banyal, R. K; Sridharan, R; Aishwarya, S (IOP Publishing, 2019-05)
    We report atmospheric turbulence parameters, namely atmospheric seeing, tilt-anisoplanatic angle (θ0) and coherence time (τ0), measured under various sky conditions, at Vainu Bappu Observatory in Kavalur. Bursts of short ...
  • Performance Evaluation of Adaptive Optics Systems 
    Sridharan, R; Raja Bayanna, A; Srivastava, N; Kumar, B; Ravindra, B; Gupta, S. K; Jain, N; Ambastha, A; Venkatakrishnan, P (Astronomical Society of India, 2003)
    Adaptive Optics (AO) systems improve the resolution of ground based telescopes and allow for long exposure images. Their performance depends on the seeing conditions at the time of observations. In this paper, we evaluate ...
  • Photometry of Solar Corona to Study the Coronal Structures 
    Chakraborty, P; Sankarasubramanian, K; Majumder, S; Rajesh Nayak, K; Sridharan, R; Jana, A. D; Rajalakshmi, G; Suresh, D; Asgekar, A; Geetha, K. P; Rajesh, C. K (Indian Institute of Astrophysics, Bangalore, 1997)
    White light images of the solar corona were taken on KODAK 2415 films using 3-inch (f/11.5) telescopes fitted with SLR cameras. Observations were made from 4 different sites spread over the totality belt by four different ...
  • Seeing measurements with the Merak Hα Telescope 
    Vishnu, Unni. C; Sridharan, R; Ravindra, B; Prabhu, K (Springer, 2021-04)
    The parameter-search method (PSM) established by Rengaswamy, Ravindra, and Prabhu (Solar Phys.294, 5, 2019) for measuring the terrestrial atmospheric seeing from long-exposure solar Hα images is further validated - through ...
  • Sporadic-E associated with the Leonid meteor shower event of November 1998 over low and equatorial latitudes 
    Chandra, H; Sharma, S; Devasia, C. V; Subbarao, K. S. V; Sridharan, R; Sastri, J. H; Rao, J. V. S. V (European Geosciences Union, 2001-01)
    Rapid radio soundings were made over Ahmedabad, a low latitude station during the period 16 20 November 1998 to study the sporadic-E layer associated with the Leonid shower activity using the KEL Aerospace digital ionosonde. ...
  • Techniques for Achieving Higher Spatial Resolution 
    Sridharan, R (Astronomical Society of India, 2002-09)
    The application of speckle and interferometric techniques for imagmg small scale solar features is studIed In detail. A computer program(speckle code) was dt!v(-joped to analyze the speckle data. The capability of the ...
  • Techniques for Achieving Higher Spatial Resolution 
    Sridharan, R (Indian Institute of Astrophysics, Bangalore, 2001-07)
  • VLTI-AMBER velocity-resolved aperture-synthesis imaging of η· Carinae with a spectral resolution of 12 000 
    Weigelt, G; Hofmann, K. H; Schertl, D; Clementel, N; Corcoran, M. F; Damineli, A; De Wit, W. J; Grellmann, R; Groh, J; Guieu, S; Gull, T; Heininger, M; Hillier, D. J; Hummel, C. A; Kraus, S; Madura, T; Mehner, A; Merand, A; Millour, F; Moffat, A. F. J; Ohnaka, K; Patru, F; Petrov, R. G; Sridharan, R; Richardson, N. D; Rivinius, T; Scholler, M; Teodoro, M; Wittkowski, M (EDP Sciences, 2016-10)
    Context. The mass loss from massive stars is not understood well. η Carinae is a unique object for studying the massive stellar wind during the luminous blue variable phase. It is also an eccentric binary with a period of ...
  • Wavelength calibration of a tunable spatial heterodyne spectrometer 
    Nirmal, K; Sridharan, R; Sriram, S; Ambily, S; Mathew, J; Mayuresh, Sarpotdar; Murthy, J; Binukumar, G; Safonova, M (SPIE-The International Society for Optical Engineering, 2018-07-06)
    Spatial Heterodyne Spectroscopy (SHS) is a relatively novel interferometric technique similar to Fourier transform spectroscopy and shares design similarities with a Michelson Interferometer. An Imaging detector is used ...

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