The East India Company having resolved to establish an observatory at Madras for promoting the knowledge of Astronomy, Geography and Navigation in India, Sir Charles Oakeley, then President of the Council had the building for the observatory completed by 1792. The Madras series of observations had commenced in 1787(1786)* through the efforts of a member of the Madras Government - William Petrie - who had in his possession two three-inch achromatic telescopes, two astronomical clocks with compound pendulums and an excellent transit instrument. This equipment formed the nucleus of instrumentation of the new observatory, which soon embarked on a series of observations of the stars, the moon, and eclipses of Jupiter's satellites, with the accurate determination of longitude, as its first concern. The pier that carried the original small transit instrument on a massive granite pillar has on it an inscription in Latin, Tamil, Telugu and Hindustani, so that " Posterity may be informed a thousand years hence of the period when the mathematical sciences were first planted by British Liberality in Asia". In any case this quotation from the first annual report of the observatory is atleast a record of the fact that astronomical activity at the Madras Observatory was indeed the first among British efforts at scientific studies in India.
The longitude of the Madras Observatory has a most important role as fundamental meridian from which observations for longitude in the Indian survey are reckoned. The accuracy with which a map of India fits into a map of the world depends solely on the accuracy of the longitude determination of the transit instrument pier at the Madras Observatory. The work of the Great Tringonometrical Survey of India commenced at Madras on April 10, 1802 when a baseline measurement, related to the Madras longitude, was made.
For over a century, the Madras Observatory continued to be the only astronomical observatory in India engaged in systematic measures of star position and brightness. Goldingham, Taylor, Jacob and Pogson were the Government astronomers who dominated activity at Madras. With a new five feet transit, Taylor completed in 1884 his catalogue of places of over 11,000 stars. Double star catalogues, measures of their separation and the determination of their orbits were Jacob's principal interest. The observatory received a new meridian circle during his tenure and with it, besides observations for the determination of star position and evaluation of proper motions, a series of observations of the satellites of Jupiter and Saturn were commenced. From 1861 until his death in 1891, N. R. Pogson as Government astronomer, in keeping with progress in the science, entered into newer areas of observations. While the transit instrument and the meridian circle were both usefully utilized for a star catalogue of 3000 stars that included standard stars, large proper motion stars, variable stars and the like, it is with the new 8 - inch Cooke equatorial that he made discoveries of asteroids and variable stars. The asteroids Asia, Sappho, Sylvia, Camilla, Vera and the Variable stars Y Virginis, U Scorpii, T Sagittari, Z Virginis, X Capricorni and R.Reticuli were all first discovered visually at Madras either with the transit instrument or by the equatorial instruments. The discovery in 1867 of the light variation of R.Reticuli by C. Raghunathachary is perhaps the first astronomical discovery by an Indian in recent history. Pogson also undertook the preparation of a catalogue and atlas of variable stars, complete with magnitude estimates made by him both of the comparison and the variable. These were edited by Turner after Pogson's death.
During this period the Madras observatory participated in observations of the important total solar eclipses that were visible from India during the nineteenth century. These were the eclipses that established the foundations of astrophysics and especially of solar physics, and in these observations the Madras observatory's contributions were most significant. The first one of August 18, 1868 created the subject of solar physics, for at this eclipse the spectroscope was used for the first time to discover the gaseous nature of the prominences. The hydrogen emission lines seen in the prominence were so strong that the French astronomer Jansen reasoned they could be seen without the eclipse. The next day at the eclipse site the speculation was proved to be correct, making it possible for daily surveys of prominences thereafter, without the need of a total eclipse.
There were several eclipse teams scattered over the path of totality for this vital eclipse. The Madras Observatory had two teams, one at Wanarpati and the other Masulipatam. Clouds at Wanarpati interfered with the success of the expedition. At Masulipatam, Pogson detected the hydrogen lines in emission, as had all the teams that had a programme of observation with the spectroscope. They also saw a bright yellow line near the position of the D lines of sodium. The line originated from a hitherto unknown element later termed helium, after the source of its earliest detection.
On June 6, 1872 an annular eclipse was visible at madras. Pogson examining the region close to the moon's limb found the bright chromospheric Spectrum flash out for a short duration on the formation and again at the breaking up of the annulus. This is the first observation on record of viewing the flash spectrum at an annular eclipse.
An Indian Observatories Committee in England advised the Secretary of State on matters pertaining to the administration of the Madras Observatory. In many respects, with no adequate staff to help him, Pogson had taken on more programmes of work than he could bring to a successful termination. There were questions raised in London in 1867 whether the Madras Observatory need be continued at all, since the British had started some other observatories in their possessions in the Southern Hemisphere. It was even recommended that the Madras Observatory should concentrate more on publication of the observations already made, than make new ones. The work of Pogson was commended on, and questions on the closure of the Madras observatory relegated to the time when Pogson would retire.
Meanwhile in May 1882, Pogson had proposed the need for a twenty - inch telescope, which could be located at a hill station in South India, engaged in photography and spectrography of the sun and the stars. The proposal received active support both in India and Britain and necessary authority given for the search of a suitable location in the southern highlands or India.
The idea of making solar observations under tropical skies soon gained ground and the search for a suitable site extended over the entire India subcontinent. In the north, Leh, Mussoorie and Dehra Dun were examined for their suitability. In the southern part, the study was confined to Kodaikanal, Kotagiri and Madras. In his recommendation to the Government of India, the Meteorological Reporter, on the basis of his two-year survey pointed out that the skies were seldom free of dust as to permit observations that called for high transparency. And so the new observatory had to be located in the southern hills, with Kodaikanal becoming the obvious choice, on the basis of performance. At the Indian Observatories Committee meeting of July 20, 1893 with Lord Kelvin in the Chair, the decision was taken to establish a Solar physics Observatory at Kodaikanal with Michie Smith as its Superintendent, the decision on the permanent site of the Astronomical observatory being deferred to a later date. The observatory was to be under the control of the Government of India instead of under the Government of Madras, as it had been for century earlier.
The last five years of the nineteenth century witnessed a rapid transformation of work from the Madras Observatory to Kodaikanal. The first observations were commenced at Kodaikanal in 1901, and these conformed to patterns in the "new astronomy" that were planned for the observatory. While the two observatories functioned together under the control of a Director at Kodaikanal, the astronomical observations at Madras were confined only to the measurement of time. The new observatory had a wide array of spectroscopic equipment specially acquired for solar studies. There were instruments to visually examine the prominences around the solar limb and the spectra of sunspots. Photographic studies included daily white light photography of the solar disc and monochromatic chromospheric pictures with the spectroheliograms in the light of ionized calcium and of hydrogen. This uninterrupted series of photographs, continue unto the present day, and form one of the most unique collections of a record of solar activity available anywhere in the world. Only two other institutions, the observatory at Meudon in Paris and the Mount Wilson observatory have a collection that spans an equivalent time interval.