Horologium (constellation)
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Horologium is a constellation of six stars faintly visible in the southern celestial hemisphere. It was first described by the French astronomer Nicolas-Louis de Lacaille in 1756 and visualized by him as a clock with a pendulum and a second hand. In 1922 the constellation was redefined by the International Astronomical Union (IAU) as a region of the celestial sphere containing Lacaille's stars, and has since been an IAU designated constellation. Horologium's associated region is wholly visible to observers south of 23°N.
Horologium constellation: showing the tangent line, or viewer's horizon, at latitude approx 23°N, which is parallel to the line of −67.04 declension, the lower declination boundary of the constellation.
The constellation Horologium as it can be seen by the naked eye
Composite image of NGC 1512 (left) and the dwarf galaxy NGC 1510
Nicolas-Louis de Lacaille
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Abbé Nicolas-Louis de Lacaille, formerly sometimes spelled de la Caille, was a French astronomer and geodesist who named 14 out of the 88 constellations. From 1750 to 1754, he studied the sky at the Cape of Good Hope in present-day South Africa. Lacaille observed over 10,000 stars using a refracting telescope.
Nicolas-Louis de Lacaille
A memorial to the Abbé de Lacaille and Thomas Maclear, at Aurora in the Western Cape of South Africa. The English portion of the inscription reads: "This is the site of the Maclear Beacon positioned in 1838 near the original North Terminal of the Arc of Meridian positioned by Abbé de Lacaille, the first surveyor to introduce Geodetic Surveying into South Africa." Open the image to see the Afrikaans portion.
Leçons elementaires d'astronomie, géométrique et physique, 1755 edition
Messier 55 is a globular cluster discovered in 16 June 1752.