Kodaikanal Observatory

Solar Tunnel Telescope
  • Telescope
  • A Grubb Parson 60 cm diameter two-mirror fused quartz coelostat mounted on 11 m tower platform directs sunlight via a flat mirror into a 60m long underground horizontal `tunnel'. A 38 cm aperture f/90 achromat forms a 34 cm diameter solar image at the focal plane. The telescope has an option to mount a 20 cm achromat which provides an f/90 beam to form a 17 cm image.

  • Main Spectrograph
  • A Littrow-type spectrograph is the main instrument at the telescope. A 20 cm diameter, 18m focal length achromat in conjunction with a 600 lines/mm grating gives 9 mm/A dispersion in the fifth order of the grating. Together with the 5.5 arcsec/mm spatial resolution of the image, it forms a high resolution set up for solar spectroscopy. Recording of the spectrum can be done photographically or with a Photometrix 1k x 1k CCD system. A large format CCD system is being procured to enhance the coverage of spectrum especially for the broad resonance lines and the nearby continuum.

  • Spectroheliograph
  • The converging solar beam from the objective can be diverted to a high dispersion spectroheliograph with Littrow arrangement using a 3.43 m achromat. The photographic camera behind the second slit is being replaced by a Raticon linear array and a data acquisition system

Last updated on: May 5, 2017