Astronomy: Determination of Time, Longitude, Latitude, and Azimuth (Google eBook)

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U.S. Government Printing Office, 1899 - Spherical astronomy - 147 pages
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Page 305 - ... error cannot exceed a certain reasonably small amount. (iv) The probability of a small error is greater than the probability of a large error. As we shall frequently have to refer to constant and systematic errors in the sequel, it will be well to have a clear conception of the meaning of these terms, A constant error is one which has the same effect upon all the observations in a series. It has the same magnitude and sign in all the observations. A systematic error is one whose sign and magnitude...
Page 320 - Hadley's quadrant of so-called 'lunar distances' the angular distance between the Moon and the Sun or one of a number of fixed stars.
Page 393 - The eyepiece micrometer was always used in the position in which increased readings of the micrometer correspond to a movement of the line of sight toward the east, when the vertical circle is to the east, and toward the west when the vertical circle is to the west.
Page 355 - TALCOTT'S METHOD. tude for differential refraction has been prepared for the argument i difference of zenith distance, or$ difference of micrometer reading, on the side, and the argument " zenith distance " on the top. The sign of the correction is the same as that of the micrometer difference. TABLE LXVIII. CORRECTION FOR DIFFERENTIAL REFRACTION. (From Appendix 14, US Coast and Geodetic Survey Report for 1880.) l'ii;. in Zenith Distance. 0 10 Zenith Distance. 20 '5...
Page 361 - Treaty ran the northern boundary from the Lake of the Woods to the Rocky Mountains, thus, for the first time, finally delimiting on the north the enormous territory purchased from France. The "Oregon question
Page 341 - ... zenith distances of two stars culminating at about the same time, and on opposite sides of the zenith. The effect of this substitution is the attainment of a much higher degree of precision, arising from the increased accuracy of a differential measurement, in general, over the...
Page 345 - ... from instability in the relative positions of different parts of the instrument; nor by less than 1m, that interval being required to take the readings upon the first star and prepare for the second star of a pair; that their difference of zenith distances shall not exceed the half length of the micrometer comb, 20...
Page 394 - The programme is then to take five pointings upon the mark; direct the telescope to the star; place the striding level in position; take three pointings upon the star with chronometer times; read and reverse the striding level; take two more pointings upon the star, noting the times; read the striding level. This completes a half-set. The horizontal axis of the telescope is then reversed in...
Page 305 - constant error" is often used loosely in contradistinction to "accidental error," in such a way as to include both strictly constant errors and systematic errors. The effect of accidental errors upon the final result may be diminished by continued repetition of the observations and by the least square method of computation.
Page 274 - ... transit. If the star transits apparently too late, the objective is too far west (if the star is above the pole), and vice versa. The slow-motion azimuth screw may then be used to reduce the azimuth error. This process of reducing the azimuth error will be much more rapid and certain if, instead of simply guessing at the movement which must be given the azimuth screw, one computes roughly what fraction of a turn must be given to it. This may be done by computing the azimuth error of the instrument...

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