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A field-glass is composed of a tube which carries at its upper extremity a convex glass called an object-glass, and at its lower extremity a second glass called ocular, to which the eye of the observer is applied. The rays from the luminous object traverse the first glass, and by refraction form an image upside down at its focus. This image is looked at with the ocular, which magnifies it.
The 20-foot interferometer designed by Messrs. These take the place of the two holes over the object-glass in our experiment. After this the course of the light is exactly as it would be if the mirrors M2, M3 were replaced by two holes over the 100-inch mirror.
I had an abundance of money, few desires that were not bounded by my illuminating mirror on one side and my object-glass on the other; what, therefore, was to prevent my becoming an illustrious investigator of the veiled worlds? It was with the most buoyant hope that I left my New England home and established myself in New York. My first step, of course, was to find suitable apartments.
By the pier railing is a bevy of little girls grouped about an ancient colored man, the very ideal old Uncle Ned, in ragged, baggy, and disreputable clothes, lazy good-nature oozing out of every pore of him, kneeling by a telescope pointed to a bunch of white sails on the horizon; a dainty little maiden, in a stiff white skirt and golden hair, leans against him and tiptoes up to the object-glass, shutting first one eye and then the other, and making nothing out of it all.
Frank McClean's 24-inch refractor, with an object-glass prism for spectroscopic work.
In telescopes it has been seen that the glass placed at the observer's eye produces the magnifying power, and the object-glass which bears this power the best is the one that has the largest diameter and the greatest focal distance. In order to magnify 48,000 times it must be much larger than those of Herschel and Lord Rosse.
By the pier railing is a bevy of little girls grouped about an ancient colored man, the very ideal old Uncle Ned, in ragged, baggy, and disreputable clothes, lazy good-nature oozing out of every pore of him, kneeling by a telescope pointed to a bunch of white sails on the horizon; a dainty little maiden, in a stiff white skirt and golden hair, leans against him and tiptoes up to the object-glass, shutting first one eye and then the other, and making nothing out of it all.
At this time Gideon Spilett, aided by Herbert, took several views of the most picturesque parts of the island, by means of the photographic apparatus found in the cases, and of which they had not as yet made any use. This apparatus, provided with a powerful object-glass, was very complete.
I have not heard that any very serious consequences were expected to follow the appearance of Coggia's comet in 1874. The great heat which prevailed during parts of the summer of 1876 was held by many to be connected in some way with a comet which some very unskilful telescopist constructed in his imagination out of the glare of Jupiter in the object-glass of his telescope.
He must have the object-glass properly adjusted in its tube, and must use the highest power; that is, the smallest eye-piece, which he intends to use in the instrument. Of course he understands that in looking directly at a star or a celestial object it must appear sharp in outline and well defined. But without long practice with good instruments, this will not give him a very definite idea.
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