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The Sun

The Sun

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About the Book
Excerpt from book: CHAPTER II THE INSTRUMENTS AND METHODS USED IN SOLAR INVESTIGATION The Telescope.?The Co-lost at. ?The Spectrum and what it Indicates.?-Spectroscopes.?The Spectroheliograph.?The Helio- micrometer.?The Comparator.?The Nature of Radiation.? Laws of Radiation.?Spectra of Different Sources.?Pyrheliom- etry.?Bolometry. For a long time the telescope and the observer's eye were the principal means of advancing solar investigation, but in the last half century a number of other less familiar instruments and physical principles have been employed, which require some explanation. The Telescope A few words may be said first as to the methods of employing the telescope. The sun is far too bright to view for any length of time with the naked eye, much less with the telescope, unless means are used for reducing the brightness. It is said that the Belgian physicist, Plateau, having looked steadily at the sun twenty seconds for the purpose of studying the after images which would be produced, lost his sight permanently in consequence. To get a rough general view of the sun a screen is often used in the manner shown in Fig. 6. The dis- pjfee depends on e power of the :to and fro in (lily obtained, ht of the tele- off undesired jtermining the I klf dc, see Monthly yciety, vol. xiv, the sun cannot Fe several ways jlescopic vision. Aperture of the Diaphragm and ryepiece, but atgreat cost of definition if the diaphragm is too small or the shade glass not perfect. A reflecting telescope, if its object mirror is left unsilvered, may require only a shade glass for visual work with the sun; and, on the other hand, the objective lens of a refractor may be thinly silvered to cut down the light. But both these expedients unfit the telescope for other purposes. There are sever...
Book Details
ISBN-13: 9780217399074
Publisher: Rarebooksclub.com
Binding: Paperback
Language: English
Returnable: N
Spine Width: 5 mm
Width: 186 mm
ISBN-10: 021739907X
Publisher Date: 20 May 2012
Height: 242 mm
No of Pages: 98
Series Title: English
Weight: 191 gr
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