File:Elements of theoretical and descriptive astronomy, for the use of colleges and academies (1901) (14783924162).jpg

Identifier: elementsoftheore00whit_0 (find matches)
Title: Elements of theoretical and descriptive astronomy, for the use of colleges and academies
Year: 1901 (1900s)
Authors: White, Charles J
Subjects: Astronomy.
Publisher: New York: J. Wiley & sons
Contributing Library: University of Florida, George A. Smathers Libraries
Digitizing Sponsor: University of Florida, George A. Smathers Libraries with support from LYRASIS and the Sloan Foundation

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ch the clock shows at that instant is noted. This is theclock time of transit, and the right ascension of the star, takenfrom the Almanac, is the true time of transit; and a comparisonof these two times will evidently give us the amount by whichthe clock is fast or slow on local sidereal time. 21. Daily Bate.—If, in a similar manner, we obtain the errorof the clock on the next or on any subsequent day, the difference these two errors will be the gain or loss of the clock in theinterval; and hence, if we divide this difference by the numberof the days and parts of days which have intervened betweenthe two observations, the quotient will be the daily gain orloss. 22. Chronograph.—The accuracy of astronomical observationsis much enhanced by recording the times of the observations bymeans of an electric current. A cylinder, about which a rollof paper is wound, is turned about on its axis with a uniformmotion by the use of appropriate machinery. A pen is pressed THE TRANSIT INSTRUMENT.
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Fig. 5. THE TRANSIT INSTRUMENT. 8J down upon the paper, and is so connected with a battery thatwhenever the circuit is broken a mark of some kind is made uponthe paper. The wires of this battery are connected with thesidereal clock in such a way that every oscillation of the pendu-lum breaks the circuit. Every second is thus recorded uponthe revolving paper. The observer also holds in his hands abreak-circuit key, with which, whenever he wishes to note thetime, he breaks the circuit, and thus causes the pen to make itsmark upon the paper. The line which the pen describes uponthe paper will be something like this: abed The equidistant marks, a, b, c, &c, are the marks caused by thependulum, and the marks A, B, C, are the marks which the penmakes when the circuit is broken by the observer. The distancefrom A to 6, B to a, &c, can be measured by a scale of equalparts, and the time of an observation can thus be obtained withina small fraction of a second. The cylinder is also move

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