{"product_id":"2940014323024","title":"Be A Stargazer - Guide to Astronomy","description":"Table of Contents:\u003cbr\u003e\u003cbr\u003eWhy Study Light?...4 \u003cbr\u003eIntroduction To Light...5\u003cbr\u003eIntroduction To Color...10\u003cbr\u003eAstronomical Instruments...14\u003cbr\u003eOur Solar System...18\u003cbr\u003eThe Sun...20\u003cbr\u003eEarth's Moon...22\u003cbr\u003ePlanets...27\u003cbr\u003eAsteroids...66\u003cbr\u003eMeteoroids...68\u003cbr\u003eComets...70\u003cbr\u003eKuiper Belt...72\u003cbr\u003eBeyond Our Solar System...74\u003cbr\u003eStars...76\u003cbr\u003eConstellations...94\u003cbr\u003eFind The Stars In The Sky...102\u003cbr\u003e\u003cbr\u003e\u003cbr\u003eASTRONOMICAL INSTRUMENTS\u003cbr\u003eTHE TELESCOPE\u003cbr\u003eSome astronomical instruments are of the simplest character, some\u003cbr\u003emost delicate and complex. When a man smokes a piece of glass, in\u003cbr\u003eorder to see an eclipse of the sun, he makes a simple instrument.\u003cbr\u003eFerguson, lying on his back and slipping beads on a string at a certain\u003cbr\u003edistance above his eye, measured the relative distances of the stars.\u003cbr\u003eRefracting Telescope\u003cbr\u003eThe use of more complex instruments commenced when Galileo\u003cbr\u003eapplied the telescope to the heavens. He cannot be said to have\u003cbr\u003einvented the telescope, but he certainly constructed his own without a\u003cbr\u003epattern, and used it to good purpose. It consists of a lens, O B (Fig.\u003cbr\u003e13), which acts as a multiple prism to bend all the rays to one point at\u003cbr\u003eR. Place the eye there, and it receives as much light as if it were as\u003cbr\u003elarge as the lens O B. The rays, however, are convergent, and the\u003cbr\u003epoint difficult to find. Hence there is placed at R a concave lens,\u003cbr\u003epassing through which the rays emerge in parallel lines, and are\u003cbr\u003ereceived by the eye. Binoculars are made upon precisely this principle\u003cbr\u003etoday, because they can be made conveniently short.\u003cbr\u003eFig. 13.—Refracting Telescope.\u003cbr\u003eIf, instead of a concave lens at R, converting the converging rays into\u003cbr\u003eparallel ones, we place a convex or magnifying lens, the minute image\u003cbr\u003eis enlarged as much as an object seems diminished when the telescope\u003cbr\u003eis reversed. This is the grand principle of the refracting telescope.\u003cbr\u003eDifficulties innumerable arise as we attempt to enlarge the\u003cbr\u003einstruments. These have been overcome, one after another.\u003cbr\u003eThe Reflecting Telescope\u003cbr\u003eThis instrument differs radically from the refracting one already\u003cbr\u003edescribed. It receives the light in a concave mirror, M (Fig. 14), which\u003cbr\u003ereflects it to the focus F, producing the same result as the lens of the\u003cbr\u003erefracting telescope. Here a mirror may be placed obliquely, reflecting\u003cbr\u003ethe image at right angles to the eye, outside the tube, in which case it\u003cbr\u003eis called the Newtonian telescope; or a mirror at R may be placed\u003cbr\u003eperpendicularly, and send the rays through an opening in the mirror at\u003cbr\u003eM. This form is called the Gregorian telescope. Or the mirror M may be\u003cbr\u003eslightly inclined to the coming rays, so as to bring the point F entirely\u003cbr\u003eoutside the tube, in which case it is called the Herschelian telescope. In\u003cbr\u003eeither case the image may be magnified, as in the refracting telescope.\u003cbr\u003eFig. 14.—Reflecting Telescope.\u003cbr\u003eReflecting telescopes are made of all sizes, up to the Cyclopean eye of\u003cbr\u003ethe Subaru telescope which is 327 inches i diameter. The form of\u003cbr\u003einstrument to be preferred depends on the use to which it is to be put.\u003cbr\u003eThe loss of light in passing through glass lenses is about two-tenths.\u003cbr\u003eThe loss by reflection is often one-half. In view of this peculiarity and\u003cbr\u003emany others, it is held that a twenty-six-inch refractor is fully equal to\u003cbr\u003eany six-foot reflector.\u003cbr\u003eThe mounting of large telescopes demands the highest engineering\u003cbr\u003eability. The whole instrument, with its vast weight , with its\u003cbr\u003eaccompanying tube and appurtenances, must be pointed as accuratley\u003cbr\u003eas a rifle, and held as steadily as the axis of the globe. To give it the\u003cbr\u003erequired steadiness, the foundation on which it is placed is sunk deep\u003cbr\u003ein the earth, far from rail or other roads, and no part of the\u003cbr\u003eobservatory is allowed to touch this support.\u003cbr\u003eWhen a star is once found, the earth swiftly rotates the telescope away\u003cbr\u003efrom it, and it passes out of the field. To avoid this, clock-work is so\u003cbr\u003earranged that the great telescope follows the star by the hour, if\u003cbr\u003erequired. It will take a star at its eastern rising, and hold it constantly\u003cbr\u003ein view while it climbs to the meridian and sinks in the west. The\u003cbr\u003ereflector demands still more difficult engineering.\u003cbr\u003eThe Spectroscope\u003cbr\u003eA spectrum is a collection of the colors which are dispersed by a prism\u003cbr\u003efrom any given light. If it is sunlight, it is a solar spectrum; if the\u003cbr\u003esource of light is a star, candle, glowing metal, or gas, it is the\u003cbr\u003espectrum of a star, candle, glowing metal, or gas. An instrument to\u003cbr\u003esee these spectra is called a spectroscope.\u003cbr\u003eConsidering the infinite variety of light, and its easy modification and\u003cbr\u003eabsorption, we should expect an immense number of spectra. A mere\u003cbr\u003eprism disperses the light so imperfectly that different orders of\u003cbr\u003evibrations, perceived as colors","brand":"Laiftllc.com","offers":[{"title":"Default Title","offer_id":47181844054256,"sku":"2940014323024","price":0.99,"currency_code":"USD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0737\/7593\/9824\/files\/2940014323024_p0.jpg?v=1763606376","url":"https:\/\/shop-qa.barnesandnoble.com\/products\/2940014323024","provider":"Barnes \u0026 Noble (DEV)","version":"1.0","type":"link"}