Celestial Chart of Venus and Mercury, c. 1742 - Johann Gabriel Doppelmayr

A celestial copper engraving by Johann Gabriel Doppelmayr, published by the Homann firm in Nuremberg around 1742. The chart explains the apparent irregularities in the movements of Venus and Mercury as observed from Earth, using 1710 as its reference year. The original hand colouring gives the reader a way to follow the separate orbits through a densely worked diagram.

The Sun occupies the centre. Around it, engraved lines plot the changing positions of Mercury, Venus and Earth. The smaller diagrams and Latin notes take the reader from the broad design to individual stages in the explanation. An allegorical vignette in the upper left of the main circle introduces a quite different scale and style of engraving.

What looks at first like a set of circles is a sequence of changing positions. The smaller diagrams isolate stages of the two planets’ apparent motion, giving the reader a way to compare a single observation with the full pattern. The hand colouring gives structure to a sheet that carries a great deal of information.

The engraving measures 48.5 × 57.5 cm on a 52.5 × 62 cm sheet. The paper is in good condition, with two small restored tears in the lower part.