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, geophysics, oceanography and volcanology are examples of disciplines for which observatories have been constructed. Th ...

owned and operated by the

Indian Institute of Astrophysics The Indian Institute of Astrophysics (IIA), with its headquarters in Bengaluru, is an autonomous research institute wholly funded by the Department of Science and Technology, Government of India. IIA conducts research primarily in the areas of ...

. It is on the southern tip of the

Palani Hills The Palani Hills are a mountain range in the southern Indian states of Tamil Nadu and Kerala. 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 with t ...

from

Kodaikanal Kodaikanal () (English: ) is a municipality and hill station in Dindigul district in the state of Tamil Nadu, India. It is situated at an altitude of in the Palani hills of the Western Ghats. Kodaikanal was established in 1845 to serve as a r ...

. 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 An electrojet is an electric current which travels around the E region of the Earth's ionosphere. There are three electrojets: one above the magnetic equator (the equatorial electrojet), and one each near the Northern and Southern Polar Circles ( ...

are made here due to the unique geography of Kodaikanal.

Ionospheric sounding In telecommunications and radio science, an ionospheric sounding is a technique that provides real-time data on high-frequency ionospheric-dependent radio propagation, using a basic system consisting of a synchronized transmitter and receiver. ...

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

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 secto ...

vertical drift and

surface A surface, as the term is most generally used, is the outermost or uppermost layer of a physical object or space. It is the portion or region of the object that can first be perceived by an observer using the senses of sight and touch, and is ...

observations are made here regularly. Summaries of the data obtained are sent to national (

India Meteorological Department India Meteorological Department (IMD) is an Indian 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 headquar ...

) and global (

World Meteorological Organization The World Meteorological Organization (WMO) is a List of specialized agencies of the United Nations, specialized agency of the United Nations responsible for promoting international cooperation on atmospheric science, climatology, hydrology an ...

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 ste ...

, proposed the need for photography and

spectrography Spectroscopy is the field of study that measures and interprets electromagnetic spectra. In narrower contexts, spectroscopy is the precise study of color as generalized from visible light to all bands of the electromagnetic spectrum. Spectrosc ...

of the sun and the stars using a

telescope A telescope is a device used to observe distant objects by their emission, Absorption (electromagnetic radiation), absorption, or Reflection (physics), reflection of electromagnetic radiation. Originally, it was an optical instrument using len ...

, 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 Northwestern Europe, off the coast of the continental mainland. It comprises England, Scotland, Wales and North ...

Secretary of State, Indian Observatories Committee, chaired by

Lord Kelvin William Thomson, 1st Baron Kelvin (26 June 182417 December 1907), was a British mathematician, Mathematical physics, mathematical physicist and engineer. Born in Belfast, he was the Professor of Natural Philosophy (Glasgow), professor of Natur ...

, 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 John Evershed CIE FRS FRAS (26 February 1864 – 17 November 1956) was an English astronomer. He was the first to observe radial motions in sunspots, a phenomenon now known as the Evershed effect. Biography Evershed was born in Gomsha ...

1906–1911 * Thomas Royds 1911–1923 * Anil Kumar Das 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 Literature, letters, judged to be "eminently distinguished in their subject". ...

1895–1911 * Charles Pritchard Butler *

1911–1923 * Thomas Royds 1923–1937 * A. L. Narayan 1937–1946 * Anil Kumar Das 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 and used to perform some of the first ever

helioseismology Helioseismology 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 surface. It is similar to geoseismol ...

investigations. Measurements of vector

magnetic fields A magnetic field (sometimes called B-field) is a physical field that describes the magnetic influence on moving electric charges, electric currents, and magnetic materials. A moving charge in a magnetic field experiences a force perpendicular ...

were initiated during the 1960s. In 1977, many of the astronomers from Kodaikanal shifted to

Bangalore Bengaluru, also known as Bangalore (List of renamed places in India#Karnataka, its official name until 1 November 2014), is the Capital city, capital and largest city of the southern States and union territories of India, Indian state of Kar ...

and established the

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 a relatively intense, localized emission of electromagnetic radiation in the Stellar atmosphere, Sun's atmosphere. Flares occur in active regions and are often, but not always, accompanied by coronal mass ejections, solar partic ...

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

digitize Digitization is the process of converting information into a digital (i.e. computer-readable) format.Collins Dictionary. (n.d.). Definition of 'digitize'. Retrieved December 15, 2021, from https://www.collinsdictionary.com/dictionary/english/ ...

d for long-term studies of the last ten solar cycles, in an effort led by

Dipankar Banerjee Dipankar Banerjee may refer to: * Dipankar Banerjee (general), Indian army general * Dipankar Banerjee (metallurgist) (born 1952), Indian metallurgist * Dipankar Banerjee (solar physicist), Indian solar physicist See also *Dibakar Banerjee Dib ...

. *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 quantitatively expresses the attribute of hotness or coldness. Temperature is measurement, measured with a thermometer. It reflects the average kinetic energy of the vibrating and colliding atoms making ...

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 eve ...

and

rainfall Rain is a form of precipitation where water droplets that have condensed from atmospheric water vapor 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. ...

are made here and transmitted to the

and the

for use in

Weather forecasting Weather forecasting or weather prediction 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 info ...

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 ...

. *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 () is a device that reflects sunlight toward a target, turning to compensate for the Sun's apparent motion. The reflector is usually a plane mirror. The target may be a physical object, distant from the heliostat, or a direct ...

refractor A refracting telescope (also called a refractor) is a type of optical telescope that uses a lens as its objective to form an image (also referred to a dioptric telescope). The refracting telescope design was originally used in spyglasses and ...

by the French

optical Optics is the branch of physics that studies the behaviour and properties of light, including its interactions with matter and the construction of instruments that use or detect it. Optics usually describes the behaviour of visible, ultravio ...

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, 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 warms and begins to release gases when passing close to the Sun, a process called outgassing. This produces an extended, gravitationally unbound atmosphere or Coma (cometary), coma surrounding ...

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 f ...

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

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

s giving 6 cm diameter full disc photographs of the sun in

K-alpha The Siegbahn notation is used in X-ray spectroscopy to name the spectral lines that are characteristic to elements. It was introduced by Manne Siegbahn. The characteristic lines in X-ray emission spectra correspond to atomic electronic transition ...

and

H-alpha Hydrogen-alpha, typically shortened to H-alpha or Hα, is a deep-red visible spectral line of the hydrogen atom with a wavelength of 656.28 nm in air and 656.46 nm in vacuum. It is the first spectral line in the Balmer series and is em ...

spectral line A spectral line is a weaker or stronger region in an otherwise uniform and continuous spectrum. It may result from emission (electromagnetic radiation), emission or absorption (electromagnetic radiation), absorption of light in a narrow frequency ...

s are in regular use. A 46 cm diameter

Foucault Paul-Michel Foucault ( , ; ; 15 October 192625 June 1984) was a French historian of ideas and philosopher who was also an author, literary critic, political activist, and teacher. Foucault's theories primarily addressed the relationships be ...

siderostat A heliostat () is a device that reflects sunlight toward a target, turning to compensate for the Sun's apparent motion. The reflector is usually a plane mirror. The target may be a physical object, distant from the heliostat, or a directi ...

feeds light to a 30 cm aperture f/22,

Cooke triplet The ''Cooke triplet'' is a photographic lens designed and patented 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 the elimination of most of the optical distort ...

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 grating with a periodic structure that diffraction, diffracts light, or another type of electromagnetic radiation, into several beams traveling in different directions (i.e., different diffractio ...

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. Wavelengths ...

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 CCD may refer to: Science and technology * Charge-coupled device, an electronic light sensor used in various devices including digital cameras * .ccd, the filename extension for CloneCD's CD image file * Carbonate compensation depth, a property ...

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 {{Short pages monitor {{Authority control Astronomical observatories in India Astronomical observatories in Tamil Nadu Kodaikanal Solar telescopes Indian Institute of Astrophysics