Johannes Kepler was a very prolific author but there is an aspect to his major books that usually doesn’t receive enough attention. As well as the torrent of words that poured from his pen, his books were always richly embellished with masterfully executed and deeply expressive illustrations. This visual communication between Kepler and his readers reached a high point in the fascinating, immensely complex frontispiece of the Tabulae Rudolphinae (Rudolphine Tables) published in Ulm in 1627. The frontispiece of this monumental collection of tables, that probably did more to further the acceptance of a heliocentric model of the cosmos than any other publication, is a complex sketch of the history of astronomy from Aratus (c. 312–240 BCE) down to Kepler himself, in the following I will narrate the story of this wonderful depiction of that history.
The concept for the illustration was from Kepler but it that was probably drawn by Wilhelm Schickard (1592–1635) from the University of Tübingen, who Kepler had first employed to provide the illustration for his Harmonice Mundi (1619); it was engraved by the Nürnberger engraver, Georg Celer (1599–1632).
It depicts the Temple of Urania, the muse of astronomy, which is here an open sided pavilion with a decagon base and a domed roof supported on ten columns. The columns are in pairs and starting from the back develop in style and materials to depict the passage of time. The first pair are simple tree trunks with the branches loped off, the second pair consists of simple stone blocks piled on top of each other. Moving towards the front there are two pairs of brick column and at the front are a pair of smooth Corinthian columns, the one on the right having an achanthus-leaf capital. The floor of the pavilion depicts the stary heavens which form the fundament on which the observations, the columns, to which we will return later, are built.
The Emperor (Rudolf) sits on his throne in the middle of the roof and above him hovers the imperial eagle, who is dropping gold coin from his beak down on the astronomers below. This element of the illustration contains more than a little irony. Throughout his time as imperial mathematicus, Kepler had extreme difficulties getting the imperial treasury to pay his wages. By the time he finally came to print the Tabulae Rudolphinae he was owed a large sum of money in back wages, some of which he tried in vain to obtain to cover the printing costs. In the end he paid the printing costs out of his own pocket and then instead of handing the finished product over to the current emperor, who property the book was, he took the whole first edition to the Frankfurt Bookfair, where he sold it to recuperate his outlay.
Around the rim of the roof are six goddesses each one representing significant aspects of Kepler’s astronomy. From left to right they are optics (the shining head of the goddess is creating a shadow of a globe), the telescope, logarithms (holding in her hands rods of the ratio of one to two, and the number around her head showing the Keplerian natural logarithm of 1/2: 0.6931472), geometry (with a compass, square-ruler and a diagram of an ellipse), ‘stathmica’, namely the laws of the lever and balance (holding a balance, with the Sun at the fulcrum and a star at the end of the longer arm, an allusion to the slowing of a planet’s motion as the magnetic force of the Sun decreases with increasing distance), and magnetics (holding a lodestone and compass).
The ceiling of the pavilion depicts the Tychonic system of the cosmos with the Earth at the centre orbited by the Moon and the Sun with the other planets orbiting the sun. Hanging down from the Earth in the middle of the pavilion is a board with the title of the book, Tabulae Rudolphinae.
The six columns at the front each represent to work of an astronomer, starting from the left Aratus (c. 312–240 BCE), Hipparchus (c. 190–c. 120 BCE), Copernicus (1473–1543), Tycho (1546–1601), Ptolemaeus (fl, 150 CE), and Meton (5th century BCE). Aratus wrote a poem, Phenomena that describes the cosmology of Eudoxus of Cnidus (c. 390–c. 340 BCE), his column is decorated with an armillary sphere. Hipparchus is, of course, next to Ptolemaeus the most important of the Greek astronomers and his column is decorated with a celestial sphere and he is depicted holding his star catalogue. Moving to the righthand side, Ptolemaeus is shown sitting whilst drawing a diagram. Part of the Greek title of the Almagest is visible and the diagram on the table in front of him shows Ptolemy’s theorem (if a quadrilateral is inscribed in a circle, then the sum of the products of its two pairs of opposite sides is equal to the product of its diagonals). Ptolemaeus’ column is decorated with an astrolabe. Behind Ptolemaeus is the column for Meton, who gave his name to the Meton cycle which aligns the solar and lunar cycles over a nineteen-year period, and amongst other things forms the basis for the Jewish lunar-solar calendar. Meton’s column is decorated with a dial displaying his cycle. At the back of the pavilion between the tree trunk columns stands a nameless Chaldean, that is Babylonian, astronomer who is measuring the angular distance between celestial bodies using his fingers.
We now move to the front and the centre of attraction framed by the two Corinthian columns. On the left sits Copernicus, his column is decorated with a Jacob’s staff and his parallactic rulers or triquetrum, which Tycho had brought to Hven. On the plinth of the column rests a tablet with observations of Regiomontanus (1436–1476) and Bernhard Walther (1430–1504), which were included in De revolutionibus. On the right stands Tyco Brahe dressed in a full-length ermine robe and wearing his Order of the Elephant medal. He is pointing out to Copernicus the model of his system of the cosmos on the ceiling. By his elbow on the plinth of his column is his Astronomiae instauratae Progymnasmata (Prague 1602/3), which was the publication of his model. His column is decorated with his quadrant and his sextant.
Underneath Copernicus and Tycho on the base of the pavilion is a panel depicting a map of Hven, the island where Tycho built his observatory, Uraniborg, where he carried out twenty years of, for the time, extremely accurate astronomical observations, the material that Kepler used to calculate the Tabulae Rudolphinae. To the right of this are two panels depicting the printing of the book. The first panel shows a pressman inking the exposed type lying on the platen. The pressman on the left has raised the frisket with his right hand and is now removing the printed sheet which he will pass to his left hand to place on the pile of printed sheets under the bed of the press, and replace it with a new sheet ready to be printed. The second panel shows a compositor setting type. The panel to the left of centre shows Kepler with a model of the roof of the pavilion and a list of some of his principal scientic texts, Mysterium Comographicum (1596), Astronomiae Pars Optica (1604), Astronomia Nova (1609), and Epitome Astronomiae Copernicanae (1618–1621). To the right of Kepler is another panel with an image of the schoolteacher and poet Johann Baptist Hebenstreit (c. 1580–1638), a friend of Kepler’s. Hebenstreit wrote a poem, ‘An idyll on the Keplerian star-spangled tower, showing depicted the birth and progress of astronomy up to our age and the quite new, long-desired and incomparable work of the Tables’, which explains the imagery of the frontispiece and which was printed as the preface to the book.
There is, of course, always the open question, just how much of this wonderful illustration could users of the Tabulae Rudolphinae actually interpret correctly.