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Updated: May 26, 2025
Assuming that the choice must fall upon a refractor, unless proper guarantees for one of the other kind should be offered, one of my first visits was to the glass firm of Chance & Co. in Birmingham, who had cast the glass disks for the Washington telescope. This firm and Feil of Paris were the only two successful makers of great optical disks in the world.
During the last decade, however, all this has been changed, and we not only have societies, such as the British Astronomical Association, setting apart a distinct section for the systematic investigation of lunar detail, but some of the largest and most perfect instruments in the world, among them the noble refractor on Mount Hamilton, employed in photographing the moon or in scrutinising her manifold features by direct observation.
Less than a fortnight later, September 23, Professor Galle, of the Berlin Observatory, received a letter from Leverrier requesting his aid in the telescopic part of the inquiry already analytically completed. He directed his refractor to the heavens that same night, and perceived, within less than a degree of the spot indicated, an object with a measurable disc nearly three seconds in diameter.
Sir Howard Grubb finished in 1893 a 28-inch achromatic for the Royal Observatory, Greenwich; the Thompson equatoreal, mounted at the same establishment in 1897, carries on a single axis a 26-inch photographic refractor and a 30-inch silvered-glass reflector; the Victoria telescope, inaugurated at the Cape in 1901, comprises a powerful spectrographic apparatus, together with a chemically corrected 24-inch refractor, the whole being the munificent gift of Mr.
The earliest chemical star-pictures were those of Castor and Vega, obtained with the Cambridge refractor in 1850 by Whipple of Boston under the direction of W. C. Bond. Double-star photography was inaugurated under the auspices of G. P. Bond, April 27, 1857, with an impression, obtained in eight seconds, of Mizar, the middle star in the handle of the Plough.
Possibly it is much distended by heat, and undoubtedly its atmosphere intercepts a very much smaller proportion of its light than in stars of the solar class. As regards Procyon, visual verification was awaited until November 13, 1896, when Professor Schaeberle, with the great Lick refractor, detected the long-sought object in the guise of a thirteenth-magnitude star. Dr.
It is superior in the first respect because a lens transmits more light than a mirror reflects. Professor Young has remarked that about eighty-two per cent of the light reaches the eye in a good refractor, while "in a Newtonian reflector, in average condition, the percentage seldom exceeds fifty per cent, and more frequently is lower than higher."
Stanley Williams's measurements and discussion of the set for 1891 showed the high value of the materials thus collected, although much more minute details can be seen than can at present be photographed. The red spot shows as "very distinctly annular" in several of these pictures. Recently, the planet has been portrayed by Deslandres with the 62-foot Meudon refractor.
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