The constellations derived from the imagination of the ancients, who attributed divine significance to every expression of Creation. Also, they needed to fix points of reference in the night sky, to mark their operations at sea and on land.
Thus Ptolemy (II century AD), in his Almagest, identified 48 constellations inspired by mythology, with the exception of Libra (the scales), the only one that "represents" an object rather than a living creature.
Originally the area it occupies belonged to the constellation of Scorpius (the scorpion), being its claws. The Zodiac only had, in fact, eleven signs in the classical era, and many were those who would rather not change that number nor the shape of Scorpius.
Virgil instead preferred the creation of a new constellation, corresponding to the time when Octavian Augustus was born, and in the Georgics intentionally tells that Scorpio crouches up to make room for Libra.
The illustrations reproduced here - representing only some constellations of the northern and southern skies - are from the third edition of Atlas Celeste / de Flamsteed, / publié en 1776 par J. Fortin, / Ingénieur-mécanicien Globes et pour les Sphères. / Troisième Edition, / Revue, et corrigée augmentée, / par MM. Delalande et Méchain. / A Paris, / Chez Delamarche, Editeur et Géographie, successeur de Robert de / Vaugondy, Rue de Jardinet No 13 (quartier St. André des Arcs).
Jean Flamsteed (1646-1719), a famous British astronomer, in 1729 published the Atlas Celeste in 28 large-size tables, showing the position of the constellations visible on the horizon of London in the year 1690. In the next edition, edited by J. Fortin, the position was established at the year 1780.
In the meantime - so states J. Fortin in his preface to the third edition of the Atlas Celeste - some new constellations were added, including Rameau et Cerbere created by J. Hevel (1611-1687) - generally known by the Latinized form of his name in Hevelius - who lived in Gdansk, where he built an observatory in 1641; he also added the Shield of Sobieski,, in 1690, in honor of his patron, King John III Sobieski of Poland, while Pierre Charles Le Monnier (1715-1799) - who studied astronomy applied to navigation - introduced the Reindeer,, in memory of the trip to the Arctic Circle of the French astronomers in 1736.
The third edition included Turdus Solitaire by Le Monnier; the Gentleman by Joseph-Jérôme Lalande (1732-1807), director of the Observatory of Paris and prolific author of astronomical studies; the Poniatowski Royal Taurus, "invented" by the Polish Poczobut; the Telescope of Herschel - (1738-1822), the astronomer who with Laplace identified the planet Uranus, by their predecessors considered a star - and the Harp of Georges, both created by Hell and published in the Ephemeris of Vienna, 1790. There also appear the Trophy of Frederick (1787), instituted by Johan Bode and the Quadrant, placed by Lalande in an empty area between the Dragon, Bootes and Hercules. Furthermore there was also added the southern planisphere (1760) by Nicolas-Louis Lacaille (1713-62), which includes 14 constellations designed to glorify the instruments of Physics, Navigation and Art, such as - for example - the Carpenter's level, the Compass, the Painter's easel, the Sculptor, the Microscope, the Air-pump, the Compass and the Sextant.
In 1922 the International Astronomical Union published an official list of 88 constellations, compiled by the Belgian astronomer Eugene Delporte, which give the final map of the night sky.
(Edited by Paola Presciuttini)