French astronomical instruments in India

Rajesh Kochhar

A six-inch aperture telescope on an English mount was made by M. Secretan of Lerebours & Secretan of Paris on an order from Capt. William Stephen Jacob (1813- 62),  who  was  then  at  Poona. The  telescope  was inspected by Jacob’s friend Charles Piazzi Smyth in 1849 at Paris, who made a painting of it that can be seen at Royal Observatory, Edinburgh.

Jacob was in the meantime appointed the director of Madras Observatory, where the telescope arrived in 1850. The East India Company subsequently payed its cost (£500) to Jacob and bought the telescope.

The telescope had a defective object glass, which was replaced by the maker in 1852. Jacob used this teles­ cope to study the brighter satellites of Saturn. He showed in August 1852 that the crepe (or C) ring discovered two years earlier was translucent so that one could see the globe of Saturn through it ‘as through a film of smoke’. The same phenomenon was independently noted in late October 1852 by William Lassell (1799-1880) at Malta through his 20-inch aperture reflecting telescope.

The revelation of the semi-transparent crepe ring convinced astronomers that the whole question of ring structure needed a thorough re-examination, and led to the influential 1857 work of James Clerk Maxwell, who showed that the rings were made of a large number of particles. Using the Secretan telescope, Norman Robert Pog­ son discovered an asteroid on 17 April 1861. It was the first ever discovery from India of a minor planet, which was aptly named Asia.

3. 6-inch aperture telescope by Lerebours & Secretan of Paris 1849, painted by Charles Piazzi Smyth. ( Courtesy Royal Observatory Edinburgh)

This telescope, along with an 8-inch equatorial by Troughton & Simms (1866), was the mainstay of the Madras Observatory. The 6-inch telescope was remodelled in 1898 by Sir Howard Grubb of Dublin, who provided it with an electric drive, and mounted an extra 5-inch aperture Grubb photographic lens on the equatorial. The remo­delled telescope was installed at the Kodaikanal Ob­servatory (established 1899). In 1912 John Evershed replaced the object glass with a photovisual lens, which in turn was replaced in 1918 by a visual achromatic lens. Since 1912 the telescope has been in regular use for direct daily photography of the sun. It is thus the oldest telescope in India – one of the oldest in the world – still in use.

A minor instrument received from France is a drum chronograph with electrical arrangement made by Eichens & Hardy of Paris, Hardy having been in charge of the electrical part. This chronograph came to Mad­ras with a history behind it.

Two identical Cooke transit telescopes (marked 1 and 2) and two chronographs (A and B) were made in 1872 under the supervision of Col. A. Strange for the Great Trigonometrical Survey of India. In 1872 itself these two sets of instruments (along with clocks by Frodsham) were used for the fist telegraphic determi­nation of longitude difference. The stations chosen were Bangalore and Madras and the observers were Maj. John Herschel and Maj. W. M. Cambell, both of Royal Engineers. (Regular work, however, started in 1875.) In 1896, the telescope 2 and the chronograph A were sent to Madras for the proposed Kodaikanal Observatory. The drum chronograph is now without the electrical apparatus, and displayed at Bangalore. (The Cooke telescope, minus the optics, continues to be at its original site at Kodaikanal.)

Photograph of the now damaged drum chrono­ graph by Eichens & Hardy of Paris 1872.

Rajesh Kochhar is an astronomer and a historian of sciences. He is also the advisor of this project.

References:

  1. Worster, W. K. & Jacob, W. S., Madras Astronomical Observatories, Volume 8, 1848-52, Madras Observatory, 1854.
  2. Kochhar, R. K., Bull. Astr. Soc. India, 13, 287 (1985). Madras Observatory: Buildings and instruments.
  3. Kochhar, R. K., Vistas in Astron. (submitted). Growth of astro­ nomical instrumentation in India.
  4. See Salwi, D. M., J. Br. Astron. Assoc., 98, 189 (1988), for an account of Madras Observatory and a recent photograph of the 6- in. telescope. For comments by the present author, see Kochhar, R. K., J. Br. Astron. Assoc., 99, 120 (1989).
  5. Alexander A. F. O’D., The planet Saturn, Faber & Faber, London, 1962.
  6. Account of the operations of the Great Trigonometrical Survey of India, Volume 9, Debra Dun, 1883.

This article is an excerpt from the original article by the author in the Journal of the British Astronomical Association (vol.101, no.2, p.95-100), reproduced here with permission from the author.

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