Its place was taken by an immensely heavier instrument, the present refractor of 28 inches' aperture, and 28 feet focal length; and that this change was effected safely was an eloquent testimony to the solidity of the original mounting.
So that, though doing nothing directly to improve the art of navigation, or to find the longitude at sea, the great photographic refractor takes its share in the work of 'Rectifying the Tables of the Planets.
In view of this peculiarity and many others, it is held that a twenty-six-inch refractor is fully equal to any six-foot reflector.
No very large refractor is entirely free from these defects.
Douglass left Boston in March, 1894, with a six-inch Clark refractor belonging to the writer, to make a test of the seeing throughout the Territory.
He directed his refractorto 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.
Dawes with the comparatively small refractor of his observatory at Wateringbury, and on December 3 was described by Mr. Lassell (then on a visit to him) as "something like a crape veil covering a part of the sky within the inner ring.
The Washington 26-inch refractordisclosed to him, under exceptionally favourable conditions, a set of equatorial belts on the disc of Neptune, and they took just the direction prescribed by theory.
An improved instrument was erected in the autumn of the same year, and the fifty-one stars, bright enough for determination with a refractor of 11 inches aperture, were promptly taken in hand.
July 27 Installation of 28-inch refractor at the Royal Observatory, Greenwich.
Harvard 15-inch refractor that daguerreotype of the moon with which the career of extra-terrestrial photography may be said to have formally opened.
Its chief instrumental glory was a refractor of fifteen inches aperture by Merz and Mahler (Fraunhofer's successors), which left the famous Dorpat telescope far behind, and remained long without a rival.
Thus the refractor and the reflector differ chiefly in their manner of gathering light.
The lens of the Yerkes' refractor measures three feet four inches in diameter, whereas the Mount Wilson reflector has a diameter of no less than eight feet four inches.
A refractoris also more convenient to handle than is a reflector.
In what follows I have only a refractor in mind, although the same principles would apply to a reflector.
The refractor achieves this by means of a carefully shaped lens, called the object glass, or objective.
The superiority of the refractor in regard to definition arises from the fact that any distortion at the surface of a mirror affects the direction of a ray of light three times as much as the same distortion would do at the surface of a lens.
In the refractor the observer looks toward the object; in the reflector he looks away from it.
In order to get around the obstacle formed by chromatic aberration it is necessary to make the object glass of a refractor consist of two lenses, each composed of a different kind of glass.
The answer is, that the refractor gives more light and better definition.
In the great Harvard refractor Vega is seen with no less than thirty-five companions.
The Andromeda nebula has been partially resolved by Lord Rosse's great reflector, and (it is said) more satisfactorily by the great refractor of Harvard College.
In order to observe the latter we therefore employ what is called a terrestrial telescope, which is merely a refractor with some extra lenses added in the eye portion for the purpose of turning the inverted image the right way up again.
In the year 1825 the largest achromatic refractor in existence was one of nine and a half inches in diameter constructed by Fraunhofer for the Observatory of Dorpat in Russia.
One of their most famous telescopes is the great Lick Refractor now in use on Mount Hamilton in California.
The largest equatorial at Greenwich is a refractorof twenty-eight inches aperture and twenty-eight feet long, constructed by Sir Howard Grubb.
Newall with the Bruce spectrograph attached to the great 25-inch Newall refractor of the Cambridge Observatory, and we have added the values found at Potsdam by Vogel and Scheiner.
It consists of a great refractor specially constructed for photography, of twenty-six inches aperture (presented by Sir Henry Thompson) and a reflector of thirty inches diameter, which is the product of Dr.
There is a limit to the size of the refractor depending upon the material of the object-glass.
A still greater effort has recently been made by the same firm in the refractor of forty inches aperture for the Yerkes Observatory of the University of Chicago.
There are four rotary domes covering the astrographic refractor in the Leonine Tower, and some excellent work is being accomplished.
As this was of immense strength, the lower walls being some five yards in thickness, it seemed strong and firm enough to support the thirteen-inch photographic refractor which was ordered from Gauthier.
Vogel observed and drew it in 1871 with the great refractor at Bothkamp.
When the successors of Dollond had carried the achromatic refractor to the limit enforced by the size of the glass disks they were able to secure, they found these instruments not so great an improvement after all.
It is not easy to say which type of telescope, the refractor or the reflector, is the more famous.
The 15 inchrefractor belonging to the Harvard College Observatory has also been employed in various experiments with a slit spectroscope, and is again being used as described below.
The twenty-four inch refractor of which I had the use was the last telescope Clark ever made, and he pronounced it his best one.
A curious instance of difference of vision was well illustrated one superb evening when Mr. Webb and the writer were observing Saturn with the nine and a half inch refractor at Hardwick.
The above list will hopefully give you a few useful examples demonstrating the appropriate usage of "refractor" in a variety of sentences. We hope that you will now be able to make sentences using this word.
