Danzig, on the Baltic, winter 1690. Johannes Hevelius, brewer and astronomer, has been dead for three years. His widow, Elisabeth Koopman, herself an astronomer, brings out the posthumous work he had prepared: the Firmamentum Sobiescianum, a celestial atlas in fifty-six plates. Each chart is engraved on copper, some over a meter wide. In it, Hevelius corrected the positions of 1,564 stars, observed with the naked eye (he refused the telescope) from the observatory he had built on his rooftop in 1641. The Firmamentum Sobiescianum dedicates seven new constellations to King John III Sobieski of Poland, who had funded the astronomer. Six of those constellations are still official today: the Lyre of the Falcon, the Sextant, the Lesser Lion, the Lynx, the Little Fox, the Shield of Sobieski.

That atlas illustrates a peculiarity of classical celestial cartography: the sky is represented in mirror, seen not from Earth but from outside the celestial sphere, the divine side as it were. The convention comes from antique celestial planispheres, and it persists in all Western astronomy up to the eighteenth century. The visual result is strange and beautiful: constellations appear as the reverse of what one sees when looking up at night. For decoration, that inversion does not matter. For the scholar of the time, it eased certain position calculations.

John Flamsteed and the Atlas Coelestis (1729)

Greenwich, near London, early eighteenth century. John Flamsteed is the first Astronomer Royal of England, appointed in 1675 by Charles II to establish the Royal Observatory of Greenwich. For forty-four years he observes the northern sky with unprecedented precision, using quadrants and refractors. He identifies 2,935 stars, nearly double Hevelius's catalogue. At his death in 1719, his catalogue is not yet published. His widow, Margaret, takes over and brings out in 1729 the Atlas Coelestis, an atlas in twenty-six double plates.

The Atlas Coelestis introduces a new feature: the sky is shown the right way, as one sees it from Earth. The constellations, drawn by James Thornhill (who also painted the dome of St. Paul's Cathedral), are allegorical figures of remarkable finesse. Perseus holds the head of Medusa. Hercules wrestles the Nemean lion. Andromeda is chained to the rock. This atlas becomes, for a century, the visual reference of European astronomy. Later editions (in 1753, 1781, 1795) reuse its plates almost without change.

The sky as allegory

Why did antique celestial charts depict constellations as mythological figures? Three reasons. First, tradition: since Ptolemy and his Almagest in the second century, Western astronomers inherit a system in which each group of stars carries the name of a hero, an animal or an object. Keeping these figures lets the knowledge pass down without reinvention. Then, memorization: it is easier to remember Orion's belt than three bright stars aligned in this region of the sky. Finally, aesthetics: the sky of the Ancients was peopled with stories, and showing those stories gave the atlas a humanist dignity.

In the nineteenth century, that convention disappears. Modern atlases adopt a stripped-down graphic style: dots for stars, lines for constellations, no figures. Friedrich Argelander in Germany, John Herschel in England, Benjamin Gould in the United States (who founds the Cordoba Observatory in Argentina in 1870) publish atlases without allegory, more precise but less beautiful. It is that tension between scientific precision and symbolic beauty that gives the seventeenth- and eighteenth-century atlases, obsolete for astronomy, a second life as decorative objects.

"An antique sky chart," astronomer Camille Flammarion wrote in 1880, "is not made to guide the eye in the sky. It is made to guide the mind in the memory of skies."

Living with a celestial chart on the wall

A celestial chart works especially well in the bedroom, above the bed or facing it. The motif soothes: a dark ground (deep blue, starry black), gilded or ivory constellations, allegories that suggest dreaming. Suggested format: 50 by 70 for a celestial planisphere, 70 by 100 for a full atlas plate or a large isolated figure. Frame: light wood or oak to warm the deep blue, or thin brass for lovers of a cabinet-of-curiosities look. Avoid the white frame, which works against the represented night.

A celestial chart also suits a child's or teenager's bedroom. The motif accompanies imagination, constellations become familiar, the sky moves closer. Plates of Pegasus, the Centaur, Orion or the Great Bear are the most recognized. They can be set as a triptych, 30 by 40 format, in identical frames. The wall becomes a small fixed observatory.

Three starting points

  • A plate from Hevelius's Firmamentum Sobiescianum (1690): sky in mirror, constellations as mythological silhouettes. For a bedroom or office in dark tones.
  • A plate from Flamsteed's Atlas Coelestis (1729): sky the right way, drawings by James Thornhill, neoclassical look. For a classic living room or a library.
  • A complete celestial planisphere bringing all the constellations together on a single round chart. For a large bedroom or a stairwell that can carry an imposing format.

At Montmartre Poster, the vintage collection offers several antique celestial charts in the lineage of that European tradition, printed on 275 gsm art paper. The deep blue and the ivory of the constellations have been calibrated on originals held by the Paris Observatory and the British Library in London.