![]() Because observing conditions changed over the many years required, the resulting Córdoba Durchmusterung, or CD, lacks the homogeneity of its northern counterpart. ![]() The Bonn survey was extended to −23° in 1886, and at Córdoba, Arg., it was carried to the parallel of −62° by 1908 and to the South Pole by 1930. The accompanying charts, published in 1863, far surpassed all former maps in completeness and reliability. The resulting Bonner Durchmusterung (1859–62), or BD catalog, contains 324,189 stars to about the ninth magnitude between declinations +90° and −2°. Keeping the telescope fixed, he recorded the stars, zone by zone, as the Earth’s rotation carried the stars past the field of view. The German word Durchmusterung, literally a “scanning through,” was introduced by Argelander, who undertook to list all the stars visible in the 8-cm Bonn refractor. Bessel in 1818, his positions are the oldest still considered useful in modern astronomy. Measurements of the third astronomer royal, James Bradley, achieved a precision within a few seconds of arc as reduced by the German astronomer Friedrich W. These observations provided the basis for his great Atlas Coelestis. His aforementioned Historia Coelestis Britannica listed 3,000 stars, exceeding all former catalogs in number and accuracy. The first astronomer royal, John Flamsteed, pioneered the use of telescopic sights for measuring stars’ positions. A comparable catalog of southern stars was not available until 1678, when the young Edmond Halley published positions of 350 stars measured during a British expedition to St. With his large and sturdy (but pre-telescopic) quadrants and sextants, he carefully measured the positions of 777 stars, to which he later added enough hastily observed stars to bring the catalog up to exactly 1,000. Near the end of the 16th century, Tycho Brahe of Denmark resolved to provide an observational basis for the renovation of astronomy. SpaceNext50 Britannica presents SpaceNext50, From the race to the Moon to space stewardship, we explore a wide range of subjects that feed our curiosity about space!.Learn about the major environmental problems facing our planet and what can be done about them! Saving Earth Britannica Presents Earth’s To-Do List for the 21st Century.Britannica Beyond We’ve created a new place where questions are at the center of learning.100 Women Britannica celebrates the centennial of the Nineteenth Amendment, highlighting suffragists and history-making politicians.COVID-19 Portal While this global health crisis continues to evolve, it can be useful to look to past pandemics to better understand how to respond today.Student Portal Britannica is the ultimate student resource for key school subjects like history, government, literature, and more.From tech to household and wellness products. Britannica Explains In these videos, Britannica explains a variety of topics and answers frequently asked questions.This Time in History In these videos, find out what happened this month (or any month!) in history.#WTFact Videos In #WTFact Britannica shares some of the most bizarre facts we can find.Demystified Videos In Demystified, Britannica has all the answers to your burning questions.Britannica Classics Check out these retro videos from Encyclopedia Britannica’s archives.
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