The series of Astronomical observations was commissioned in 1711 by the Bolognese count Luigi Marsili. He had the artist Donato Creti paint all the planets in as many small pictures and made a gift of these to the Pope to convince him of the importance for the Holy Church of an astronomical observatory. The gift made it possible to achieve his goal, because with the support of Clement XI (pontiff from 1700 to 1721) the first public astronomical observatory was opened in Bologna a short time later. The eight small canvases show the planetary system as it was then known: the Sun (cat.40432), the Moon (cat.40433), Mercury (cat.40434), Venus (cat.40435), Mars (cat.40436), Jupiter (cat.40437), Saturn (cat.40438) and a Comet (cat.40439). The planet Uranus, only discovered in 1781, is missing. The presence of the planets is dominant in the composition. They are depicted as observed with telescopes and various optical instruments (for which the artist had precise instructions) by small human figures in eighteenth century clothes, reabsorbed into the vastness of the nocturnal scene.