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Updated: June 7, 2025
An instrument on the principle of Dawes' solar eyepiece has been suggested; this, if used with an invariable and absolute scale of tints, would remove many difficulties attending these investigations. The scale which was adopted by Schroter, and which has been used by selenographers up to the present time, is as follows:
Quen-lung obediently placed the eyepiece to his eye, and a few seconds later Frobisher observed the man turn pale and stagger backward, almost dropping the telescope as he did so. The man's eyes were dilated, his face turned the colour of putty; his lower lip had dropped, and his hands were trembling as though palsied.
Beams of light from a star, entering by the slits, unite at the focus of the telescope, where the image is examined by an eyepiece magnifying about five thousand diameters. Across the enlarged star image a series of fine, sharp fringes is seen, even when the atmospheric conditions are poor. If the star is single the fringes remain visible, whatever the distance between the slits.
Draper suggested a very excellent plan for testing a flat surface, which I briefly describe. It is a well known truth that, if an artificial star is placed in the exact center of curvature of a truly spherical mirror, and an eyepiece be used to examine the image close beside the source of light, the star will be sharply defined, and will bear very high magnification.
Myriads of such stars, invisible to the unassisted eye, were rendered perfectly distinct by the aid of the telescope. The magnificence of the sight was vastly increased when the telescope was directed to any portion of the Milky Way. It revealed such countless multitudes of stars that I had only to sit before the eyepiece, and behold the endless procession of these glorious objects pass before me.
The precious possession now arrived; and although the sight of it of the brasses on which her hand had often rested, of the eyepiece through which her dark eyes had beamed engendered some decidedly bitter regrets in him for a time, he could not long afford to give to the past the days that were meant for the future.
But in reckoning magnifying power, diameter, not area, is always considered. For practical use an eyepiece composed of an ordinary single lens is seldom advantageous, because good definition can only be obtained in the center of the field.
With such an eyepiece the image viewed is beyond the farther or field lens instead of between the two lenses, and as this fact renders it easier to adjust wires or lines for measuring purposes in the focus of the eyepiece, the Ramsden construction is used when a micrometer is to be employed.
He felt a great respect, even tenderness, for this taciturn, high-principled, devoted scientist. He had never seen him excited, hardly ever aroused. He was a man of figures, whose only passion seemed to be the "music of the spheres." A long silence followed, during which Thornton seemed to bend more intently than ever over his eyepiece. The hand of the big clock slipped gradually to midnight.
Under the magnifying effect of the eyepiece lens Benson could see the beach, the flag-bedecked hotels, and the moving masses of people on the shore. Yet, all this time, he was out at sea, more than a mile from the beach. The periscope itself, if seen from a boat an eighth of a mile away, would undoubtedly have been taken for a floating bottle. "Let me have a peep," demanded Somers.
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