File:Astronomy for high schools and colleges (1881) (14577162058).jpg

Identifier: astronomyforhigh00newc (find matches)
Title: Astronomy for high schools and colleges
Year: 1881 (1880s)
Authors: Newcomb, Simon, 1835-1909 Holden, Edward Singleton, 1846-1914, joint author
Subjects: Astronomy
Publisher: New York, H. Holt and Company
Contributing Library: The Library of Congress
Digitizing Sponsor: The Library of Congress

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Text Appearing Before Image:
Fig. 28.—a transit instrument. and from the times of these transits as read from theclock to determine either the corrections of the clock orthe right ascension of the observed body, as explained inChapter I., § 5. THE TRANSIT INSTRUMENT. lb It has two general forms, one (Fig. 28) for use in fixedobservatories and one (Fig. 29) for use in the field. It consists essentially of a telescope T T (Fig. 28)mounted on an axis Y V 2X right angles to it.
Text Appearing After Image:
Fig. 29. -PORTABLE TRANSIT INSTRUMENT. The ends of this axis terminate in accurately cylindricalsteel pivots A\hich rest in metallic bearings V F, in shapelike the letter Y, and hence called the Ys. 76 ASTRONOMY. These are fastened to two pillars of stone, brick, oriron. Two counterpoises W W are connected with theaxis as in the plate, so as to take a large portion of theweight of the axis and telescope from the Ys, and thus todiminish the friction upon these and to render the rota-tion about Y V more easy and regular. In the ordinaryuse of the transit, the line Y Yh placed accurately leveland perpendicular to the meridian, or in the east and westline. To effect this ^ adjustment, there are two sets ofadjusting screws, by which the ends of T^ F in the Ys maybe moved either up and down or north and south. Theplate gives the form of transit used in permanent observa-tories, and shows the observing chair C, the reversing car-riage Rj and the level L. The arms of the latter haveYs, which

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