The Kodaikanal Solar Observatory is a

solar Solar may refer to: Astronomy * Of or relating to the Sun ** Solar telescope, a special purpose telescope used to observe the Sun ** A device that utilizes solar energy (e.g. "solar panels") ** Solar calendar, a calendar whose dates indicate t ...

observatory An observatory is a location used for observing terrestrial, marine, or celestial events. Astronomy, climatology/meteorology, geophysical, oceanography and volcanology are examples of disciplines for which observatories have been constructed. His ...

owned and operated by the Indian Institute of Astrophysics. It is on the southern tip of the

Palani Hills The Palani Hills are a mountain range in the southern Indian states of Kerala and Tamil Nadu. The Palani Hills are an eastward extension of the Western Ghats ranges, which run parallel to the west coast of India. The Palani Hills adjoin the hi ...

from

Kodaikanal Kodaikanal () is a hill station which is located in Dindigul district in the state of Tamil Nadu, India. Its name in the Tamil language means "The Gift of the Forest". Kodaikanal is referred to as the "Princess of Hill stations" and has a long ...

town. The

Evershed effect The Evershed effect, named after the British astronomer John Evershed, is the radial flow of gas across the photospheric surface of the penumbra of sunspots from the inner border with the umbra towards the outer edge. The speed varies from around 1 ...

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 geography of Kodaikanal. Ionospheric soundings,

geomagnetic Earth's magnetic field, also known as the geomagnetic field, is the magnetic field that extends from Earth's interior out into space, where it interacts with the solar wind, a stream of charged particles emanating from the Sun. The magnetic fi ...

F region The F region of the ionosphere is home to the F layer of ionization, also called the Appleton–Barnett layer, after the English physicist Edward Appleton and New Zealand physicist and meteorologist Miles Barnett. As with other ionospheric sectors ...

vertical drift and surface observations are made here regularly. Summaries of the data obtained are sent to national (

India Meteorological Department The India Meteorological Department (IMD) is an agency of the Ministry of Earth Sciences of the Government of India. It is the principal agency responsible for meteorological observations, weather forecasting and seismology. IMD is headquarter ...

) and global (

World Meteorological Organization The World Meteorological Organization (WMO) is a specialized agency of the United Nations responsible for promoting international cooperation on atmospheric science, climatology, hydrology and geophysics. The WMO originated from the Internati ...

Global Atmosphere Watch The Global Atmosphere Watch (GAW) is a worldwide system established by the World Meteorological Organizationa United Nations agencyto monitor trends in the Earth's atmosphere. It arose out of concerns for the state of the atmosphere in the 1960s. ...

) data centers. They have a full-time staff of two scientists and three technicians.

History

As early as 1881, Mr. Blanford, then Meteorological Reporter to the Government of India, recommended "the improvement of the work of solar observations in order to obtain accurate measures of the sun’s heating power at the earth’s surface and its periodic variations". In May 1882, the government astronomer at Madras,

Norman Robert Pogson Norman Robert Pogson, CIE (23 March 1829 – 23 June 1891) was an English astronomer who worked in India at the Madras observatory. He discovered several minor planets and made observations on comets. He introduced a mathematical scale of stel ...

, proposed the need for photography and

spectrography Spectroscopy is the field of study that measures and interprets the electromagnetic spectra that result from the interaction between electromagnetic radiation and matter as a function of the wavelength or frequency of the radiation. Matter wa ...

of the sun and the stars using a twenty-inch

telescope A telescope is a device used to observe distant objects by their emission, absorption, or reflection of electromagnetic radiation. Originally meaning only an optical instrument using lenses, curved mirrors, or a combination of both to observe ...

, which could be at a hill station in South India. On 20 July 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. The United Kingdom of Great Britain and Northern Ireland, commonly known as the United Kingdom (UK) or Britain, is a country in Europe, off the north-western coast of the continental mainland. It comprises England, Scotland, Wales and North ...

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 The Madras Observatory was an astronomical observatory which had its origins in a private observatory set up by William Petrie in 1786 and later moved and managed by the British East India Company from 1792 in Madras (now known as Chennai). The ...

to Kodaikanal and the observatory was founded on 1 April 1899. The first observations were commenced at Kodaikanal in 1901. Partial List of Assistant Directors * John Evershed 1906–1911 *

Thomas Royds Thomas Royds (April 11, 1884 – May 1, 1955) was a British solar physicist who worked with Ernest Rutherford on the identification of alpha radiation as the nucleus of the helium atom, and who was Director of the Kodaikanal Solar Observatory, I ...

1911–1923 *

Anil Kumar Das Anil Kumar Das FRAS, FNI (1 February 1902 - 18 February 1961) was an Indian scientist, astronomer. During the International Geophysical Year, observatories in Madrid, India, and Manila were responsible for monitoring solar effects. The Kodaikan ...

1937–1946 List of Directors * Charles Michie Smith

FRSE Fellowship of the Royal Society of Edinburgh (FRSE) is an award granted to individuals that the Royal Society of Edinburgh, Scotland's national academy of science and letters, judged to be "eminently distinguished in their subject". This soci ...

1895–1911 * John Evershed 1911–1923 *

1923–1937 * A. L. Narayan 1937–1946 *

1946–1960 * M. K. Vainu Bappu 1960–1982 * J.C.Bhattacharya 1982-1990 * Ramnath Cowsik 1992 - 2003 * S.Siraj Hasan 2006 - 2012 * P.Sreekumar 2013 - 2018 * Annapurni Subramanian 2019–Present A 12 m solar tower with modern spectrograph was established in 1960 by

Amil Kumar Das Anil Kumar Das FRAS, FNI (1 February 1902 - 18 February 1961) was an Indian scientist, astronomer. During the International Geophysical Year, observatories in Madrid, India, and Manila were responsible for monitoring solar effects. The Kodaikan ...

and used to perform some of the first ever

helioseismology Helioseismology, a term coined by Douglas Gough, is the study of the structure and dynamics of the Sun through its oscillations. These are principally caused by sound waves that are continuously driven and damped by convection near the Sun's surfa ...

investigations. Measurements of vector magnetic fields were initiated during the 1960s. In 1977, many of the astronomers from Kodaikanal shifted to

Bangalore Bangalore (), officially Bengaluru (), is the capital and largest city of the Indian state of Karnataka. It has a population of more than and a metropolitan population of around , making it the third most populous city and fifth most ...

and established the Indian Institute of Astrophysics.

Current activities

Areas of current interest at the observatory are *Observations and interpretation of the morphological changes in active regions and their role in occurrence of transients such as

solar flares A solar flare is an intense localized eruption of electromagnetic radiation in the Sun's atmosphere. Flares occur in active regions and are often, but not always, accompanied by coronal mass ejections, solar particle events, and other solar phe ...

. *Study of contributing factors to chromospheric calcium K indices. *Measurement of vector magnetic fields. *Photographs of ~ 117 years are being

digitize DigitizationTech Target. (2011, April). Definition: digitization. ''WhatIs.com''. Retrieved December 15, 2021, from https://whatis.techtarget.com/definition/digitization is the process of converting information into a digital (i.e. computer- ...

d for long-term studies of the last ten solar cycles, in an effort led by Dipankar Banerjee. *Studies on the structure and dynamics of the equatorial ionosphere and its response to the solar and interplanetary variability are being carried out. *Studies of the equatorial electrojet and of the structure and dynamics of the equatorial ionosphere and its response to solar and interplanetary variability are being made. *Hourly observation of surface

temperature Temperature is a physical quantity that expresses quantitatively the perceptions of hotness and coldness. Temperature is measured with a thermometer. Thermometers are calibrated in various temperature scales that historically have relied o ...

pressure Pressure (symbol: ''p'' or ''P'') is the force applied perpendicular to the surface of an object per unit area over which that force is distributed. Gauge pressure (also spelled ''gage'' pressure)The preferred spelling varies by country and e ...

and

rainfall Rain is water droplets that have condensed from atmospheric water vapor and then fall under gravity. Rain is a major component of the water cycle and is responsible for depositing most of the fresh water on the Earth. It provides water f ...

are made here and transmitted to the

and the

for use in

Weather forecasting Weather forecasting is the application of science and technology forecasting, to predict the conditions of the Earth's atmosphere, atmosphere for a given location and time. People have attempted to predict the weather informally for millennia a ...

and research in the

atmospheric sciences Atmospheric science is the study of the Earth's atmosphere and its various inner-working physical processes. Meteorology includes atmospheric chemistry and atmospheric physics with a major focus on weather forecasting. Climatology is the study of ...

. *Public education about astronomy including tours of the facility, access to the astronomy library, nighttime telescopic sky viewing, and presentation of specialized university-level courses, seminars and workshops.

Equipment

Full disc imaging

A 15 cm aperture English-mounted

Heliostat A heliostat (from ''helios'', the Greek word for ''sun'', and ''stat'', as in stationary) is a device that includes a mirror, usually a plane mirror, which turns so as to keep reflecting sunlight toward a predetermined target, compensating ...

refractor A refracting telescope (also called a refractor) is a type of optical telescope that uses a lens (optics), lens as its objective (optics), objective to form an image (also referred to a dioptrics, dioptric telescope). The refracting telescope d ...

by the French optical firm of Lerebours et Secretan of Paris, acquired in 1850 and remodeled to 20 cm by Grubb-Parsons in 1898 to serve as a

photoheliograph A solar telescope is a special purpose telescope used to observe the Sun. Solar telescopes usually detect light with wavelengths in, or not far outside, the visible spectrum. Obsolete names for Sun telescopes include heliograph and photoheliograp ...

, has been in use since the early 1900s to obtain daily 20 cm white light pictures of the sun, sky permitting. The 20 cm refractor is used occasionally for

comet A comet is an icy, small Solar System body that, when passing close to the Sun, warms and begins to release gases, a process that is called outgassing. This produces a visible atmosphere or coma, and sometimes also a tail. These phenomena ar ...

ary and

occultation An occultation is an event that occurs when one object is hidden from the observer by another object that passes between them. The term is often used in astronomy, but can also refer to any situation in which an object in the foreground blocks ...

observations and sometimes made available to visitors for night sky viewing. Twin

spectroheliograph The spectroheliograph is an instrument used in astronomy which captures a photographic image of the Sun at a single wavelength of light, a monochromatic image. The wavelength is usually chosen to coincide with a spectral wavelength of one of the ch ...

s giving 6 cm diameter full disc photographs of the sun in K-alpha and H-alpha

spectral line A spectral line is a dark or bright line in an otherwise uniform and continuous spectrum, resulting from emission or absorption of light in a narrow frequency range, compared with the nearby frequencies. Spectral lines are often used to iden ...

s are in regular use. A 46 cm diameter

Foucault Foucault may refer to: *Foucault (surname) *Léon Foucault (1819–1868), French physicist. Three notable objects were named after him: **Foucault (crater), a small lunar impact crater ** 5668 Foucault, an asteroid **Foucault pendulum *Michel Fouca ...

siderostat feeds light to a 30 cm aperture f/22,

Cooke triplet The Cooke triplet is a photographic lens designed and patented (patent number GB 22,607) in 1893 by Dennis Taylor who was employed as chief engineer by T. Cooke & Sons of York. It was the first lens system that allowed elimination of most of th ...

lens. The two prism K-alpha spectroheliographs were acquired in 1904 and the H-alpha

diffraction grating In optics, a diffraction grating is an optical component with a periodic structure that diffracts light into several beams travelling in different directions (i.e., different diffraction angles). The emerging coloration is a form of structura ...

spectroheliograph was operational in 1911. Since 1912, prominent pictures over the full limb are 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 An achromatic lens or achromat is a lens that is designed to limit the effects of chromatic and spherical aberration. Achromatic lenses are corrected to bring two wavelengths (typically red and blue) into focus on the same plane. The most comm ...

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.

Solar tunnel telescope

A Grubb Parson 60 cm diameter two-mirror fused quartz

coelostat A solar telescope is a special purpose telescope used to observe the Sun. Solar telescopes usually detect light with wavelengths in, or not far outside, the visible spectrum. Obsolete names for Sun telescopes include heliograph and photoheliograph ...

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 An optical spectrometer (spectrophotometer, spectrograph or spectroscope) is an instrument used to measure properties of light over a specific portion of the electromagnetic spectrum, typically used in spectroscopic analysis to identify mate ...

is the main instrument of the telescope. A 20 cm diameter, 18 m focal length

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

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.

Ionosondes

The lab is equipped for studying the

ionospheric The ionosphere () is the ionized part of the upper atmosphere of Earth, from about to above sea level, a region that includes the thermosphere and parts of the mesosphere and exosphere. The ionosphere is ionized by solar radiation. It plays an im ...

and geomagnetic effects of solar activity. A NBS C3 analogue ionosonde was installed in 1955, for vertical soundings of the ionosphere. Quarterly soundings were made round the clock. In 1993, a

digital Digital usually refers to something using discrete digits, often binary digits. Technology and computing Hardware *Digital electronics, electronic circuits which operate using digital signals **Digital camera, which captures and stores digital i ...

ionosonde model IPS 42/DBD43 was commissioned enabling five minute or better sounding rates.

Other facilities

high frequency High frequency (HF) is the ITU designation for the range of radio frequency electromagnetic waves (radio waves) between 3 and 30 megahertz (MHz). It is also known as the decameter band or decameter wave as its wavelengths range from one to ten ...

Doppler radar was built indigenously and made operational to study F-region

Skywave In radio communication, skywave or skip refers to the propagation of radio waves reflected or refracted back toward Earth from the ionosphere, an electrically charged layer of the upper atmosphere. Since it is not limited by the curvature of ...

dynamics. A lacour

magnetometer A magnetometer is a device that measures magnetic field or magnetic dipole moment. Different types of magnetometers measure the direction, strength, or relative change of a magnetic field at a particular location. A compass is one such device, o ...

and a Watson magnetometer were installed and have been used regularly at the observatory since the early 1900s. They also have a broadband

seismograph A seismometer is an instrument that responds to ground noises and shaking such as caused by earthquakes, volcanic eruptions, and explosions. They are usually combined with a timing device and a recording device to form a seismograph. The output ...

GPS The Global Positioning System (GPS), originally Navstar GPS, is a Radionavigation-satellite service, satellite-based radionavigation system owned by the United States government and operated by the United States Space Force. It is one of t ...

receiver and magnetic variometers. The observatory has a popular astronomy

museum A museum ( ; plural museums or, rarely, musea) is a building or institution that cares for and displays a collection of artifacts and other objects of artistic, cultural, historical, or scientific importance. Many public museums make these ...

on campus for the visitors. The displays are mainly pictorial, with a few models, a live solar image and the Fraunhofer spectrum also presented. The

library A library is a collection of materials, books or media that are accessible for use and not just for display purposes. A library provides physical (hard copies) or digital access (soft copies) materials, and may be a physical location or a vir ...

is one of the observatory's 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 are often used for national and international meetings, workshops and classes for up to 40 participants on subjects such as Kodaikanal Summer School in Physics, the Kodai-Trieste Workshop on Plasma Astrophysics and the Solar Physics Winter School.Indian Institute of Astrophysics, 2006 ''Solar Physics Winter School'', retrieved 3/13/200

/ref>

References

External links

Indian Institute of Astrophysics, Kodaikanal Observatory
retrieved 3/13/2007 * ttp://www.ias.ac.in/resonance/Aug2002/pdf/Aug2002p16-28.pdf Madras and Kodaikanal Observatories : A Brief Historybr>Cambridge University Library: Royal Greenwich Observatory Archives, Kodaikanal Solar Observatory, archive papers 1892-1963
retrieved 3/13/2007. *Further reading: Antia H. M., Bhatnagar A., Ulmschneider P. (ed.s) (2006) ''Lectures on Solar Physics (Lecture Notes in Physics)'', Cambridge University Press, New York, 335 page
Excerpts
retrieved 3/13/2007 {{Authority control Astronomical observatories in India Astronomical observatories in Tamil Nadu Kodaikanal Astronomy Telescopes Solar telescopes Indian Institute of Astrophysics