The Henry Brothers 33” Refractor at Meudon was used by many famous astronomers. However one of its greatest claims to fame relates to the work done by E.M. Antoniadi, in dispelling the idea of manmade ‘Martian Canals’. Eugène Michel Antoniadi (March 1, 1870 – February 10, 1944) was a Greek astronomer, born in Asia Minor, who spent most of his life in France. He was also known as Eugenios Antoniadis. His name is also sometimes given as Eugène Michael Antoniadi or even (incorrectly) as Eugène Marie Antoniadi. He became a highly reputed observer of Mars, and at first supported the notion of Percival Lowell’s Martian canals, but after using the 33” ‘Grand Lunette’ at Meudon Observatory during the 1909 opposition of Mars, he came to the conclusion that canals were an optical illusion. In 1909 Henri Deslandres, the director of the Meudon Observatory placed the Grand Lunette---then, as now, the largest refractor in Europe, and the third largest in the world---at his disposal for the favourable opposition. On September 20th, 1909, he made his first observations with the Grand Lunette. There was a temperature inversion that night over Paris; the air had arranged itself into stratified layers that remained stable for seven hours, allowing images of Mars that were simply glorious. It is supremely ironic that Antoniadi's first views of the planet with the large instrument were to prove the best of his career. "The first glance cast at the planet on September 20 was a revelation," he wrote. "The planet appeared covered with a vast and incredible amount of detail held steadily, all natural and logical, irregular and chequered, from which geometry was conspicuous by its complete absence." A "maze of complex markings" covered the south part of Syrtis Major, which was then approaching the central meridian; the deserts of Libya and Hesperia appeared shaded, and Mare Tyrrhenum looked "like a leopard skin." He described the land between Syrtis Major and Hellas as being "like a green meadow, sprinkled with tiny white spots of various sizes, and diversified with darker or lighter shades of green." He later told Lowell that after he got over his initial excitement at the "bewildering" amount of detail visible, "I sat down and drew correctly both with regard to form and intensity all the markings visible. . . . However, one third of the minute features I could not draw; the task being beyond my means.” Five days after these breathtaking views of the planet, Antoniadi wrote excitedly to W. H. Wesley, secretary of the Royal Astronomical Society: "I have seen Mars more detailed than ever, and I pronounce the general configuration of the planet to be very irregular, and shaded with markings of every degree of darkness. Mars appeared in the giant telescope very much like the Moon, or even like the aspect of the Earth's surface such as I saw it in 1900 from a balloon at a great height (12,000 feet)." He continued to observe and draw the planet. He pointed out to Lowell that "the tremendous difficulty was not to see the detail, but accurately to represent it. There, my experience in drawing proved of immense assistance." Again he emphasized that the detail he was seeing was not in the least geometric; it was highly irregular and completely natural in appearance. "Bewildering" was the word he would use again and again in describing it. Antoniadi was a skilled observer; he was able to make out faint tones and subtle colours on the planet that were inaccessible in smaller instruments. In general, Antoniadi found the best seeing at Meudon on nights when it was foggy and quiet. But he enjoyed few nights with perfect seeing---he later estimated only one night in fifty. On most evenings the image was "more or less boiling," but during the less agitated moments of the boiling image the large aperture revealed more than a smaller one would have done. Indeed, good images were "preceded by a period of slight rippling of the disk, very detrimental to the detection of fine detail. The undulations would then cease suddenly, when the perfectly calm image of Mars revealed a host of bewildering details.” Such was his experience on the nights of October 6 and November 9, when he enjoyed brief periods of excellent definition in which he grasped the true character of the Martian deserts. "The soil of the planet then appeared covered with a vast number of dark knots and chequered fields," he wrote, "diversified with the faintest imaginable dusky areas, and marbled with irregular, undulating filaments, the representation of which was evidently beyond the powers of any artist.” “There was nothing geometrical in all this, nothing artificial, the whole appearance having something overwhelmingly natural about it." In the desert known as Amazonis he had held some of this detail for ten to twelve seconds at a time. Instead of the "hideous lines" that were wont to appear in brief glimpses under conditions of indifferent seeing, he made out "a maze of knotted, irregular, chequered streaks and spots." Even held thus steadily, the features were so complex that Antoniadi despaired of drawing them, though he provided Lowell an impressionistic sketch of what he had seen. There is a striking similarity between this sketch and the Mariner 9 and Viking imagery, the resemblance of the pattern of windblown streaks around cratered terrain to Antoniadi's sketch being highly suggestive of the real structure of the surface on this part of the planet. With regard to the canals, Antoniadi believed that, in some cases, there was at least some objective basis to their fleeting apparitions. The Jamuna, which to Schiaparelli had appeared on June 9, 1890, as a narrow line, appeared in the Grand Lunette as "nothing like a regular band . . . but rather the mere irregular border of a weak halftone." Other canals were similarly found to consist of "winding, irregular knotted streaks, or broad irregular bands, or groups of complex shadings, or isolated dusky spots, or jagged edges of half-tones." Antoniadi thus felt that his work had provided a partial vindication of Schiaparelli's observations, but he thought otherwise of Lowell’s spider webs; those he regarded as absolutely illusory.
Paul Pierre Henry was born on the 21st August, 1848 at Nancy, France. He and his younger brother Prosper Henry (born 10th December 1849) grew up to become two of the greatest pioneers of Astrophotography and were also responsible for the construction of some of the finest telescopes ever made. The two brothers were inseparable and worked together throughout their lives in close collaboration. Little is known of their early life save that they came from a modest family, and were educated at a local Catholic School. They began their careers as opticians working in their home town of Nancy. In 1864 they came to Paris, and began work at the Paris Observatory in the Department of Meteorology, Paul in 1864 and Prosper a year later. In 1868 they were promoted to assistant astronomers by Urbain Le Verrier, then Director of the Observatory. In 1871 Delaunay who succeeded Le Verrier as Director, recognized the Henry Brothers talent for optics and transferred them to the Department of Astronomy. In 1871 they began the task of completing the late Jean Chacornac’s charts of the Ecliptic, begun in 1852, but not completed. The work involved competing 72 charts, each 13” square covering a 50 field of view containing stars down to magnitude 13. They became alarmed at the number of stars they found in the region of the Milky Way. There were so many stars that to chart them visually was impossible. They then began experimenting with photography as a means to speed up the process. Their work on the ecliptic charts brought an added bonus; between them they found a total of 14 asteroids, the first Liberatrix discovered in September 1872. In August of 1884 their results were presented to the French Academy Sciences by Admiral Amedee Mouchez then Director of the Paris Observatory. Such was the success of their work that they commissioned to construct a 13.4” (33cm) Photographic Refractor. In the field of Astrophotography their greatest contribution came in 1885-6, when they were the first to take successful photographs of the planets, when they imaged Jupiter and Saturn. Prior to this time others had tried including contemporary pioneers like Warren de La Rue, but failed; his images of 1857 were only ½ mm across, and were therefore barely visible! During the course of their career the Henry Brothers continued to construct telescopes, and in collaboration with the engineer Paul Gauthier produced some of the finest ever made. In particular they were responsible for the 30” Refractor at the Nice Observatory and the great 32.7” Refractor at the Paris Observatory at Meudon. Paul Henry died on the 4th January 1905 at Montrouge on the outskirts of Paris, after suffering a thrombosis in his brain. His beloved brother Prosper had died 18 months earlier after a climbing accident whilst on holiday at Pralognan, in Savoy on the 25th July 1903. The Henry Brothers received many awards during their lifetime, but it is probably the naming of the lunar crater Henry Frères which would have pleased them the most. In recognition of the work of Paul Henry and his brother Prosper, the Minor Planet Centre, two asteroids were named after them ‘P.P. Henry’ and ‘P.M. Henry’. In life they were inseparable in death they are remembered forever on the surface of the Moon with a single crater.
In 1868 Pierre Janssen, then Director of the Paris Observatory went to India to observe a Total Eclipse of the Sun. It was here that Janssen ironically found a way of observing solar prominences without the need for a Total Eclipse. This remarkable discovery also led the French Government to consider establishing a Solar Physics Observatory where Janssen could continue his work. The construction of the new observatory was delayed by the Franco-Prussian war of 1870 and the siege of the French Commune. It was not until October 1876 that Janssen took up residence at the Chateau at Meudon, which was later to become the Paris Astrophysical Observatory – the principal site of the present Paris Observatory. The new Meudon Observatory lacked a telescope befitting its status as one of the world’s leading scientific institutions. In 1889 this situation was resolved with the completion of the construction of a new refractor known as the ‘Grande Lunette”. The telescope was a joint collaboration between the Henry Brothers Paul and Prosper who provided the optics - a 32.7” (83cm) visual achromatic objective; and the engineer Paul Gautier who constructed the tube, mounting and drive. In 1891, the telescope was made into an Equatorial Doublet with the addition of 24.4” Photographic Refractor both OTAs sharing the same mount. The resulting telescope at the time of its construction was only second in size to the 36” Lick Refractor, but the largest in Europe (an honour it still holds). Today the “Grand Lunette” is still in use and remains the third largest refractor in the World, behind those at the Lick (36”) and Yerkes (40”) observatories.
The ‘Grande Lunette’ at Meudon had the following Specification: Type: Equatorial Doublet Refractor Aperture: Visual 32.7” (83cm); Photographic 24.4” (62cm) Achromatic Doublets; Optics: Paul and Prosper Henry; Focal Length: 53’ (Visual) Focal Ratio: f19.5 (Visual); Mount: German Equatorial by Paul Gautier; Constructed: 1889 (Visual); 1891 (Photographic).
Meudon 33-inch Refractor
32.7" Visual; 24.4" Photographic Achromatic Doublet
Paul & Prosper Henry; Paul Gautier
Meudon, Paris, France
Meudon, Paris, France