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      Permanent link:
      https://www.ias.ac.in/article/fulltext/joaa/013/01/0129-0144

    • Keywords

       

      CCD photometry; CCD spectroscopy; system gain; readout noise

    • Abstract

       

      The system gain of two CCD systems in regular use at the Vainu Bappu Observatory, Kavalur, is determined at a few gain settings. The procedure used for the determination of system gain and base-level noise is described in detail. The Photometrics CCD system at the 1-m reflector uses a Thomson-CSF TH 7882 CDA chip coated for increased ultraviolet sensitivity. The gain is programme-selected through the parameter ‘cgain’ varying between 0 and 4095 in steps of 1. The inverse system gain for this system varies almost linearly from 27.7 electrons DN-1 at cgain = 0 to 1.5 electrons DN-1 at cgain = 500. The readout noise is ≲ 11 electrons at cgain = 66. The Astromed CCD system at 2.3-m Vainu Bappu Telescope uses a GEC P8603 chip which is also coated for enhanced ultraviolet sensitivity. The amplifier gain is selected in discrete steps using switches in the controller. The inverse system gain is 4.15 electrons DN-1 at the gain setting of 9.2, and the readout noise ∼ 8 electrons.

    • Author Affiliations

       

      T. P. Prabhu1 Y. D. Mayya1 2 G. C. Anupama1 3

      1. Indian Institute of Astrophysics, Bangalore - 560034
      2. Joint Astronomy Programme, Department of Physics, Indian Institute of Science, Bangalore - 560 012
      3. Inter-University Centre for Astronomy and Astrophysics, Ganeshkhind, Post Bag 4, Pune - 411007
    • Dates

       
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