|Organization||Indian Institute of Astrophysics|
|Altitude||2,343 meters (7,687 ft)|
|Coelostat||60 cm reflector|
|Grubb-Parsons||20 cm refractor|
The Kodaikanal Solar Observatory is an solar observatory owned and operated by Indian Institute of Astrophysics. It is located on the southern tip of the Palni Hills 4 km from Kodaikanal town, Dindigul district, Tamilnadu state, South India.
The Evershed effect was first detected at this observatory in January 1909. Solar data collected by the lab is the oldest continuous series of its kind in India. Precise observations of the equatorial electrojet are made here due to the unique geographic location of Kodaikanal.
Ionospheric soundings, geomagnetic, F region vertical drift and surface observations are made here regularly and summaries of the data obtained are sent to national IMD and global WMO GAW data centers..
They have a full time staff of two scientists and nineteen technicians.
On July 20, 1893 following a famine in Madras Presidency, which underscored the need for a study of the sun to better understand monsoon patterns, a meeting of the U.K. Secretary of State, Indian Observatories Committee, chaired by Lord Kelvin, decided to establish a Solar physics Observatory at Kodaikanal, based on its southern, dust free, high altitude location. Michie Smith was selected to be Superintendent. Starting in 1895 there was a rapid transfer of work and equipment from the Madras Observatory to Kodaikanal and the Observatory was founded on April 1, 1899.
The first observations were commenced at Kodaikanal in 1901. In 1955, ionosonde and geomagnetic facilities were installed at the Kodaikanal Observatory. A 12 m solar tower with modern spectrograph was established in 1960 by Amil Kumar Das and used to perform some of the first ever helioseismology investigations. Measurements of vector magnetic fields were initiated during the 1960s. In 1977, many of the astronomers from Kodaikanal shifted to Bangalore and established the Indian Institute of Astrophysics.
Twin spectroheliographs giving 6 cm diameter full disc photographs of the Sun in K-alpha and H-alpha spectral lines are in regular use. A 46 cm diameter Foucault siderostat feeds light to a 30 cm aperture f/22, Cooke triplet lens. The two prism K-alpha spectroheliographs were acquired in 1904 and the H-alpha Diffraction grating spectroheliograph was operational in 1911. Since 1912, prominent pictures over the full limb are also being obtained in K by blocking the solar disc. These observations and the white light pictures are obtained around 200 days a year.
Light from the 46 cm siderostat is diverted to a 15 cm Zeiss achromat objective which provides an f/15 beam and a 2 cm image. A prefilter and a daystar Ca K narrow band filter are used together with a Photometrix 1k x 1k CCD to record the K filtergram. Regular observations began in 1996. Besides synoptic observations, temporal sequences are being obtained on days of good to excellent seeing.
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 60 m 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.
A Littrow-type spectrograph is the main instrument of the telescope. A 20 cm diameter, 18 m 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.
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
A lacour magnetometer and a Watson magnetometer were installed and have been used regularly at the observatory since the early 1900s.
The library at the Observatory is one of its proud possessions. It has a collection of astronomical literature, which is of archival value. The library maintains a skeletal collection of current literature in Solar and Solar Terrestrial Physics.
The modern meeting and accommodation facilities of the observatory are often used for national and international meetings, workshops and classes for up to 40 participants on related subjects such as: Kodaikanal Summer School in Physics, the Kodai-Trieste workshop on Plasma Astrophysics and the Solar Physics Winter School