Outlines Of Astronomy - Part One

SIR JOHN F. W. HERSCHEL PART ONE NEW YORK F. COLLIER SON M C M I I SCIENCE SIR JOHN HERSCHEL SIB JOHN FREDEBICK WILLIAM HERSCHEL, BART., tlie illustrious astronomer, was the only son of Sir JB William Herschel. He was born at Slough, Bucking hamshire, England, in the year 1792. His scholastic education began at Eton, whence, at the age of seven teen, he was sent to St. Johns College, Cambridge, where he attained to great eminence in mathematics. After leaving the University, he entered upon the study of astronomy, and in 1820, assisted by his father, com pleted a mirror of 18 inches diameter and 20 feet focal length for a reflecting telescope. This, as subsequently improved, became the instrument which enabled hirn to effect the astronomical observations that formed the basis of his fame. In 1821-28 he undertook the re-examina tion of his fathers double stars. For this work he re ceived in 1826 the gold medal of the Astronomical So ciety, and the Lalande Medal of the French Institute. From 1824 to 1827 he was Secretary o the Eoyal So ciety, and in 1827 was elected to the Chair of the As tronomical Society, which office he filled on two subse quent occasions. In 1831 the honor of knighthood was conferred on him by William IV., and he subsequently 3 4 SIB JOHN HERSCHEL was made a baronet. His exploration of the southern heavens constituted an epoch in astronomy, and secured for him the distinction of memberships in almost every important society in both hemispheres. His Outlines of Astronomy, 7 here reproduced, first appeared in 1849, and, notwithstanding the disadvantage arising from the practice of stereotyping text-books which relate to pro gressive sciences, there is no moreinstructive volume extant on the subject of which it treats. Sir John Her schel died in 1871 his remains are interred in West minster Abbey, close to the grave of Sir Isaac Newton. CONTENTS PREFACE TO THE FIRST EDITION ........ 11 PREFACE TO THE FIFTH EDITION, ., . .15 PREFACE TO THE TENTH EDITION . . ., . .18 INTRODUCTION ....., , . 21 PART I CHAPTER I General Notions Apparent and real Motions Shape and Size of the Earth The Horizon and its Dip The Atmosphere Refraction Twilight Appearances resulting from Diurnal Motion From Change of Station in General Parallactic Motions Terrestrial Parallax That of the Stars Insensible First Step toward forming an Idea of the Distance of the Stars Oopernican Yiew of the Earths Motion Relative Mo tion Motions partly Real, partly Apparent G-eocenLric Astronomy, or Ideal Reference of Phenomena to the Earths Centre as a Common Conventional Station. . . . . . . . .32 CHAPTER H Terminology and Elementary Geometrical Conceptions and Relations Ter minology relating to the Globe of the Earth To the Celestial Sphere Celestial Perspective 89 CHAPTER HI Of the Nature of Astronomical Instruments and Observations in General Of Sidereal and Solar Time Of the Measurements of Time Clocks, Chronometers Of Astronomical Measurements Principle of Telescopic Sights to Increase the Accuracy of Pointing Simplest Application of this Principle The Transit Instrument Of tfoje Meas urement of Angular Intervals Methods of Increasing th. 0 Accuracy of Beading The Ternier The Microscope Of the Mural Gkele The 5 6 CONTENTS Meridian Circle Fixation of Polar and Horizontal Points The Level, Plumb-line, Artificial Horizon Principle of Collimation Collimators of Eittenhouse, Katerand Bohnenberger Of Compound Instruments with Co-ordinate Circles The Equatorial, Altitude and Azimuth In strument Theodolite Of the Sextant and Reflecting Circle Principle of Repetition Of Micrometers Parallel Wire Micrometer Principle of the Duplication of Images The Heliometer Double Refracting Eye-piece Yariable Prism Micrometer Of the Position Micrometer Illumination of Wires Solar Telescope and Bye - piece Helioscopy Collimation of large Reflectors .....