Page:Practical astronomy (1902, John Wiley & Sons).djvu/16

 vill CONTENTS. PAGE Notes on this Method. 1. Ephemeris Star Preferable to Sun 84 2. Advantage of Combining the Results from Two Stars 84 3. Advantage of Selecting Stars Distant from Zenith 84 4. Reduction of Mean Solar to Sidereal Intervals 80 5. To Determine the Reduction to the Meridian 87 THE ZENITH TELESCOPE. Description of the Zenith Telescope 00 The Attached Level and Declination Micrometer 91 4th Method. By Opposite and Nearly Equal Meridian Zenith Distances. Captain Talcott's Method (Form 9) 96 Conditions for Selecting a Pair of Stars 97 Preliminary Computations 97 Adjustment of Zenith Telescope 98 Observations 99 Reduction of Observations 99 1. Reduction from Mean Declination to Apparent Declination of the Date 99 2. The Micrometer and Level Corrections 100 3. The Refraction Correction 102 4. The Correction for Observations off the Meridian 103 I* To Determine the Reduction for an Instrument in the Meridian. . . 105 5th Method. By Polaris off the Meridian (Form 10) 109 6th Method. By Equal Altitudes of Two Stars (Form 11) 114 LONGITUDE. 1st Method. By Portable Chronometers 118 2d Method. By the Electric Telegraph (Form 12) 121 Reduction of the Time Observations (Form 12a) 125 3? Personal Equation 127 f 1 Application of Weights and Probable Error of Result 128 3d Method. By Lunar Culminations 132 Observations and Reductions 135 Equation of Transit Instrument Applicable to this Method. .. 137 4th Method. By Lunar Distances 140 1. Correction for Moon's Augmented Semi-diameter 141 2. Correction for Refraction, 142 3. Correction for Earth's Oblateness 142 Explanation of this Method 142 Observations, 148 f 1 To Find Augmentation of Moon's Semi-diameter 149 fr To Deduce the Parallax for the Point R 151 ! To Determine the Correction for Earth's Oblateness 151
 * To Determine the Probable Error of the Final Result 106
 * To Deduce the Law of Refractive Distortion 150