The Great Telescope, (of 52 Feet focus. 6 feet clear opening of Speculum.)Erected at Birr Castle in Ireland by the Earl of Rosse, President of the Royal Society. Lord Rosse directing the Conveyance of the Great Speculum to iits position at the base of the Tube, North Side.
Tinted lithograph, image area 324 x 495mm. 12¾ x 19½". Sheet 470 x 629m. 18½ x 24¾". Two tears in title and one in left margin.
The real race for aperture was launched by William Parsons, the third Earl of Rosse. The Earl was a man of vast wealth, who owned extensive estates in Ireland. He was a passionate amateur astronomer, and like most amateurs, he needed a larger telescope. Money was not a hindrance for the Earl. He wanted to build the world's largest telescope, and he wanted it to be used by professional astronomers who would be able to properly access the discoveries which would be made. He decided to attempt a mirror six feet in diameter. The project began in 1843, but had to be suspended in 1845 due to the Great Potato Famine. By 1847 conditions had improved, and the telescope was finally placed into service. The team of professional astronomers which the Earl had engaged was headed by Sir Robert Ball.The telescope proved to be of amazing optical quality. But its light-gathering capacity was beyond all expectation. For the first time it was possible to detect stars as faint as 18th magnitude. The first subject of detailed examination was the Moon. Minute craters and rills which had never before been glimpsed were charted. Delicate new details were seen on Jupiter, Saturn, and Mars. After about one year of intensive study of the solar system, the telescope was turned to the stars. The big question which astronomers were asking in the mid-Nineteenth Century was 'Are the nebulae composed of minute stars which we cannot resolve because of their extreme distance?' The great telescope provided the first opportunity to try for a meaningful answer. It was not known at this time that there were different kinds of nebulae – some composed of stars, and some composed of gas and dust. After the Earl's death in 1867, his son, the Fourth Earl of Rosse continued his father's work. He fitted the telescope with a clock drive, and expanded the research with other (smaller) special-purpose instruments. Research on the heat content of the Moon was carried out over a 22-year period. The last observations were made with the 72' in 1878, and it was dismantled in 1908. It is interesting to note that this instrument was not surpassed in size until the 100' Hooker telescope at Mt. Wilson was placed in service in 1917.
[Ref: 1421] £790.00