Identifier: elementsofastro00youn (find matches)Title: The elements of astronomy; a textbookYear: 1919 (1910s)Authors: Young, Charles A. (Charles Augustus), 1834-1908 Young, Anne Sewell, b. 1871., edSubjects: Astronomy ConstellationsPublisher: Boston, New York (etc.) Ginn and CompanyContributing Library: The Library of CongressDigitizing Sponsor: The Library of CongressView Book Page: Book ViewerAbout This Book: Catalog EntryView All Images: All Images From BookClick here to view book online to see this illustration in context in a browseable online version of this book.Text Appearing Before Image:Fig. 117.—A Spiral Nebula (Keeler). 346 PHOTOGRAPHS OF NEBULJ3. (§471 Thus, in the Pleiades, it has been found that nearly all the largeistars have wisps of nebulous matter attached to them, as indicated bythe dotted outlines in Fig. 115: and in a small territory in and nearText Appearing After Image:Fig. 118. — Mr. Robertss Photograph of the Nebula of Andromeda. the constellation of Orion, Pickering, with an eight-inch photographictelescope, found upon his star plates nearly as large a number of § 4711 CHANGES IN NEBULAE. 347 new nebulae as of those that were previously known within the sameboundary. The photographs of nebulae require, generally, an exposure of fromone hour to four or five, or even more. The images of all the brighterstars in the field are therefore enormously over-exposed, and seriouslyinjure the picture from an artistic point of view. 472. Changes in Nebulae.—It cannot perhaps be stated withcertainty that sensible changes have occurred in any of the nebulae,since they first began to be observed, — the early instruments were soinferior to the modern ones that the older drawings cannot be trustedvery far; but some of the differences between the older and more re-cent representations make it extremely probable that real changes aregoing on. Probably after aNote About ImagesPlease note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original work.