Stargazing Past and Present by J Norman Lockyer PDF
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Project Gutenberg's Stargazing: Past and Present, by J. Norman Lockyer This eBook is for the use of anyone anywhere in the United States and most other parts of the world at no cost and with almost no restrictions whatsoever. You may copy it, give it away or re-use it under the terms of the Project Gutenberg License included with this eBook or online at www.gutenberg.org. If you are not located in the United States, you'll have to check the laws of the country where you are located before using this ebook. Title: Stargazing: Past and Present Author: J. Norman Lockyer Release Date: September 30, 2016 [EBook #53172] Language: English Character set encoding: UTF-8 *** START OF THIS PROJECT GUTENBERG EBOOK STARGAZING: PAST AND PRESENT *** Produced by Richard Tonsing, Chris Curnow and the Online Distributed Proofreading Team at http://www.pgdp.net (This file was produced from images generously made available by The Internet Archive) STARGAZING: PAST AND PRESENT R. S. NEWALL’S TELESCOPE. STARGAZING: PAST AND PRESENT. BY J. NORMAN LOCKYER, F.R.S., CORRESPONDENT OF THE INSTITUTE OF FRANCE. EXPANDED FROM SHORTHAND NOTES OF A COURSE OF ROYAL INSTITUTION LECTURES, WITH THE ASSISTANCE OF G. M. SEABROKE, F.R.A.S. London: MACMILLAN AND CO. 1878. [The Right of Translation and Reproduction is Reserved.] LONDON: R. CLAY, SONS, AND TAYLOR, BREAD STREET HILL, E.C. PREFACE. In the year 1870 I gave a course of eight Lectures on Instrumental Astronomy at the Royal Institution. The Lectures were taken down by a shorthand writer, my intention being to publish them immediately. In this, however, I was prevented by other calls upon my time. In 1875 my friend Mr. Seabroke generously offered to take the burden of preparing the notes for the press off my shoulders; I avail myself of this opportunity of expressing my very great obligations to him for his valuable services in this particular as well as for important help in the final revision of the proofs. On looking over the so completed MSS., however, I saw that the eight hours at my disposal had not permitted me to touch upon many points of interest which could hardly be omitted from the book. Besides this, the progress made in the various instrumental methods in the interval, and the results obtained by them, had been very remarkable. I felt, therefore, that the object I had in view, namely, to further the cause of physical astronomy, by creating and fostering, so far as in me lay, a general interest in it, and by showing how all departments of physical inquiry were gradually being utilized by the astronomer, would only be half attained unless the account were more complete. I have, therefore, endeavoured to fill up the gaps, and have referred briefly to the new instruments and methods. The autotype of the twenty-five inch refractor is the gift of my friend Mr. Newall, and I take this opportunity of expressing my obligation to him, as also to Messrs. Cooke, Grubb and Browning for several of the woodcuts with which the chapters on the Equatorial are illustrated; and to Mr. H. Dent-Gardner for some of those illustrating Clock and Chronometer Escapements, and for revising my account of them. Nor can I omit to thank Mr. Cooper for the pains he has taken with the woodcuts, especially those copied from Tycho Brahe’s description of his Observatory, and Messrs. Clay for the careful manner in which they have printed the book. J. NORMAN LOCKYER. November 16th, 1877. v vi CONTENTS. BOOK I. THE PRE-TELESCOPIC AGE. CHAP. PAGE I.— The Dawn of Stargazing 1 II.— The First Instruments 16 III.— Hipparchus and Ptolemy 25 IV.— Tycho Brahe 37 BOOK II. THE TELESCOPE. V.— The Refraction of Light 55 VI.— The Refractor 73 VII.— The Reflection of Light 90 VIII.— The Reflector 100 IX.— Eyepieces 109 X.— Production of Lenses and Specula 117 XI.— The “Optick Tube” 139 XII.— The Modern Telescope 152 BOOK III. TIME AND SPACE MEASURERS. XIII.— The Clock and Chronometer 175 XIV.— Circle Reading 211 XV.— The Micrometer 218 BOOK IV. MODERN MERIDIONAL OBSERVATIONS. vii viii XVI.— The Transit Circle 233 XVII.— The Transit Clock and Chronograph 253 XVIII.— “Greenwich Time,” and the Use Made of It 271 XIX.— Other Instruments Used in Astronomy of Precision 284 BOOK V. THE EQUATORIAL. XX.— Various Methods of Mounting Large Telescopes 293 XXI.— The Adjustments of the Equatorial 328 XXII.— The Equatorial Observatory 337 XXIII.— The Siderostat 343 XXIV.— The Ordinary Work of the Equatorial 349 BOOK VI. ASTRONOMICAL PHYSICS. XXV.— The General Field of Physical Inquiry 371 XXVI.— Determination of the Light and Heat of the Stars 377 XXVII.— The Chemistry of the Stars: Construction of the Spectroscope 386 XXVIII.— The Chemistry of the Stars (continued): Principles of Spectrum Analysis 401 XXIX.— The Chemistry of the Stars (continued): The Telespectroscope 422 XXX.— The Telepolariscope 441 XXXI.— Celestial Photography.—The Ways and Means 454 XXXII.— Celestial Photography (continued): Some Results 463 XXXIII.— Celestial Photography (continued): Recent Results 469 ix LIST OF ILLUSTRATIONS. FIG. PAGE 1. The heavens according to Ptolemy 3 2. The zodiac of Denderah 7 3. Illustration of Euclid’s statements 10 4. The plane of the ecliptic 13 5. The plane of the ecliptic, showing the inclination of the earth’s axis 14 6. The first meridian circle 20 7. The first instrument graduated into 360° (west side) 21 8. Astrolabe (armillæ æquatoriæ of Tycho Brahe) similar to the one contrived by Hipparchus 26 9. Ecliptic astrolabe (the armillæ zodiacales of Tycho Brahe), similar to the one used by Hipparchus 28 10. Diagram illustrating the precession of the equinoxes 31 11. Revolution of the pole of the equator round the pole of the ecliptic caused by the precession of the equinoxes 32 12. The vernal equinox among the constellations, B.C. 2170 34 13. Showing how the vernal equinox has now passed from Taurus and Aries 34 14. Instrument for measuring altitudes 35 15. Portrait of Tycho Brahe (from original painting in the possession of Dr. Crompton, of Manchester) 39 16. Tycho Brahe’s observatory on the island of Huen 43 17. Tycho Brahe’s system 46 18. The quadrans maximus reproduced from Tycho’s plate 48 19. Tycho’s sextant 50 20. View and section of a prism 56 21. Deviation of light in passing at various incidences through prisms of various angles 57 22. Convergence of light by two prisms base to base 59 23. Formation of a lens from sections of prisms 60 24. Front view and section of a double convex lens 61 25. Double concave, plane concave, and concavo-convex lenses 61 xi xii 26. Double convex, plane convex, and concavo-convex lenses 62 27. Convergence of rays by convex lens to principal focus 62 28. Conjugate foci of convex lens 63 29. Conjugate images 64 30. Diagram explaining Fig. 29 64 31. Dispersion of rays by a double concave lens 65 32. Horizontal section of the eyeball 66 33. Action of eye in formation of images 68 34. Action of a long-sighted eye 69 35. Diagram showing path of rays when viewing an object at an easy distance 70 36. Action of short-sighted eye 71 37. Galilean telescope 73 38. Telescope 75 39. Diagram explaining the magnifying power of object-glass 76 40. Scheiner’s telescope 78 41. Dispersion of light by prism 80 42. Diagram showing the amount of colour produced by a lens 81 43. Decomposition and recomposition of light by two prisms 83 44. Diagram explaining the formation of an achromatic lens 84 45. Combination of flint- and crown-glass lenses in an achromatic lens 86 46. Diagram illustrating the irrationality of the spectrum 87 47. Diagram illustrating the action of a reflecting surface 91 48. Experimental proof that the angle of incidence = angle of reflection 92 49. Convergence of light by concave mirror 94 50. Conjugate foci of convex mirror 94 51. Formation of image of candle by reflection 95 52. Diagram explaining Fig. 51 96 xiii 53. Reflection of rays by convex mirror 98 54. Reflecting telescope (Gregorian) 101 55. Newton’s telescope 102 56. Reflecting telescope (Cassegrain) 103 57. Front view telescope (Herschel) 103 58. Diagram illustrating spherical aberration 105 59. Diagram showing the proper form of reflector to be an ellipse 106 60. Huyghens’ eyepiece 110 61. Diagram explaining the achromaticity of the Huyghenian eyepiece 111 62. Ramsden’s eyepiece 112 63. Erecting or day eyepiece 113 64. Images of planet produced by short and long focus lenses, &c. 123 65. Showing in an exaggerated form how the edge of the speculum is worn down by polishing 128 65*. Section of Lord Rosse’s polishing machine 131 66. Mr. Lassell’s polishing machine 132 67. Simple telescope tube, showing arrangement of object-glass and eyepiece 140 68. Appearance of diffraction rings round a star when the object-glass is properly adjusted 141 69. Appearance of same object when object-glass is out of adjustment 141 70. Optical part of a Newtonian reflector of ten inches aperture 143 71. Optical part of a Melbourne reflector 143 72. Mr. Browning’s method of supporting small specula 144 73. Support of the mirror when vertical 146 74. Division of the speculum into equal areas 147 75. Primary, secondary, and tertiary systems of levers shown separately 148 76. Complete system consolidated into three screws 148 77. Support of diagonal plane mirror (Front view) 150 78. Support of diagonal plane mirror (Side view) 150 xiv 79. A portion of the constellation Gemini seen with the naked eye 154 80. The same region, as seen through a large telescope 155 81. Orion and the neighbouring constellations 156 82. Nebula of Orion 157 83. Saturn and his moons 160 84. Details of the ring of Saturn 161 85. Ancient clock escapement 177 86. The crown wheel 178 87. The clock train 180 88. Winding arrangements 181 89. The cycloidal pendulum 185 90. Graham’s, Harrison’s, and Greenwich pendulums 188 91. Greenwich clock: arrangement for compensation for barometric pressure 194 92. The anchor escapement 197 93. Graham’s dead beat 199 94. Gravity escapement (Mudge) 200 95. Gravity escapement (Bloxam) 202 96. Greenwich clock escapement 204 97. Compensating balance 207 98. Detached lever escapement 208 99. Chronometer escapement 209 100. The fusee 209 101. Diggs’ diagonal scale 213 102. The vernier 214 103. System of wires in a transit eyepiece 220 104. Wire micrometer 221 105. Images of Jupiter 224 106. Object-glass cut into two parts 225 107. The parts separated, and giving two images of any object 225 108. Double images seen through Iceland spar 227 109. Diagram showing the ordinary and extraordinary rays in a crystal of Iceland spar 227 110. Crystals of Iceland spar 228 111. Double image micrometer 229 112. Tycho Brahe’s mural quadrant 235 113. Transit instrument (Transit of Venus Expedition) 236 114. Transit instrument in a fixed observatory 237 115. Diagram explaining third adjustment 239 116. The mural circle 241 117. Transit circle, showing the addition of circles to the transit instrument 242 118. Perspective view of Greenwich transit circle 243 119. Plan of the Greenwich transit circle 245 120. Cambridge (U.S.) meridian circle 248 121. Diagram illustrating how the pole is found 249 122. Diagram illustrating the different lengths of solar and sidereal day 255 123. System of wires in transit eyepiece 257 124. The Greenwich chronograph. (General view) 261 125. Details of the travelling carriage which carries the magnets and prickers. (Side view and view from above) 262 126. Showing how on the passage of a current round the soft iron the pricker is made to make a mark on the spiral line on the cylinder 263 127. Side view of the carriage carrying the magnets and the pointer that draws the spiral 263 128. Wheel of the sidereal clock, and arrangement for making contact at each second 266 129. Arrangement for correcting mean solar time clock at Greenwich 268 130. The chronopher 276 xv 131. Reflex zenith tube 286 132. Theodolite 288 133. Portable alt-azimuth 289 134. The 40-feet at Slough 294 135. Lord Rosse’s 6-feet 295 136. Refractor mounted on alt-azimuth tripod for ordinary star-gazing 296 137. Simple equatorial mounting 298 138. Cooke’s form for refractors 300 139. Mr. Grubb’s form applied to a Cassegrain reflector 301 140. Grubb’s form for Newtonians 303 141. Browning’s mounting for Newtonians 304 142. The Washington great equatorial 309 143. General view of the Melbourne reflector 312 144. The mounting of the Melbourne telescope 313 145. Great silver-on-glass reflector at the Paris observatory 316 146. Clock governor 319 147. Bond’s spring governor 320 148. Foucault’s governor 323 149. Illuminating lamp for equatorial 325 150. Cooke’s illuminating lamp 326 151. Dome 338 152. Drum 338 153. New Cincinnati observatory—(Font elevation) 338 154. Cambridge (U.S.) equatorial 339 155. Section of main building—United States naval observatory 341 156. Foucault’s siderostat 344 157. The siderostat at Lord Lindsay’s observatory 348 xvi 158. Position circle 353 159. How the length of a shadow thrown by a lunar hill is measured 354 160. The determination of the angle of position of the axis of Saturn’s ring 358 161. Measurement of the angle of position of the axis of a figure of a comet 359 162. Double star measurement 360 163. Ring micrometer 368 164. Thermopile and galvanometer 374 165. Rumford’s photometer 378 166. Bouguer’s photometer 379 167. Kepler’s diagram 387 168. Newton’s experiment, showing the different refrangibilities of colours 388 169. First observation of the lines in the solar spectrum 391 170. Solar spectrum 392 171. Student’s spectroscope 393 172. Section of spectroscope 394 173. Spectroscope with four prisms 396 174. Automatic spectroscope (Grubb’s form) 397 175. Automatic spectroscope (Browning’s form) 397 176. Last prism of train for returning the rays 398 177. Spectroscope with returning beam 399 178. Direct-vision prism 399 179. Electric lamp 404 180. Electric lamp arranged for throwing a spectrum on a screen 405 181. Comparison of the line spectra of iron, calcium, and aluminium, with common impurities 406 182. Coloured flame of salts in the flame of a Bunsen’s burner 408 183. Spectroscope arranged for showing absorption 409 184. Geissler’s tube 413 185. Spectrum of sun-spot 415 186. Diagram explaining long and short lines 416 187. Comparison of the absorption spectrum of the sun with the radiation spectra of iron and calcium, with common impurities 418 188. Comparison prism 423 189. Comparison prism 423 190. Foucault’s heliostat 424 191. Object-glass prism 426 192. The eyepiece end of the Newall refractor 427 193. Solar telespectroscope (Browning’s form) 428 194. Solar telespectroscope (Grubb’s form) 428 195. Side view of spectroscope 429 196. Plan of spectroscope 429 197. Cambridge star spectroscope elevation 430 198. Cambridge spectroscope plan 430 199. Direct-vision star spectroscope (Secchi) 431 200. Types of stellar spectra 433 201. Part of solar spectrum near F 436 202. Distortions of F line on sun 438 203. Displacement of F line on edge of sun 439 204. Diagram showing the path of the ordinary and extraordinary ray in crystals of Iceland spar 445 205. Appearance of the spots of light on the screen shown in the preceding figure, allowing the ordinary ray to pass and rotating the second crystal 446 206. Appearance of spots of light on screen on rotating the second crystal, when the extraordinary ray is allowed to pass through the first screen 447 207. Instrument for showing polarization by reflection 448 208. Section of plate-holder 456 209. Enlarging camera 458 210. Instantaneous shutter 460 xvii xviii 211. Photoheliograph as erected in a temporary observatory for photographing the transit of Venus in 1874 461 212. Copy of photograph taken during the eclipse of 1869 474 213. Part of Beer and Mädler’s map of the moon 476 214. The same region copied from a photograph by De La Rue 477 215. Comparison between Kirchhoff’s map and Rutherfurd’s photograph 480 216. Arrangement for photographically determining the coincidence of solar and metallic lines 481 217. Telespectroscope with camera for obtaining photographs of the solar prominences 482 BOOK I. THE PRE-TELESCOPIC AGE. STARGAZING: PAST AND PRESENT xix xx 1
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