A compendium of astronomy; containing the elements of the science, familiarly explained and illustrated, with the latest discoveries. Adapted to the use of schools and academies, and of the general reader (1850)
Olmsted, Denison, 1791-1859 · New York, R. B. Collins · leaf 87
k of the sun isAB. Consequently, before the spot can appear againon the limb from which it set out, it must describe somuch more than an entire revolution as equals the arcAA, and this occupies nearly two days, which sub-tracted from 21\ days, makes the suns revolution onits axis about 25J days ;… … 107. How large a telescope is sufficient to view the spots onthe sun ? How is the eye protected from the glare of the sunslight 1 How may these shades be made ? SOLAR SPOTS. 75 tunity he may have, to view them for himself. For ob-servations on the sun, telescopes are usually furnishedwith colored…
Astronomy
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