Name: Apianus’s ‘The Emperor's Astronomy’
Author: Petrus Apianus

This book was fabulously expensive to produce and prohibitively expensive to buy. Nicholas Wotton (an English cleric) reported in 1544 from the 'Diet of Speyer' that Apianus would give King Henry VIII a copy, for otherwise he would not be able to afford it. Edmund Halley tried in vain to obtain a copy.

 of the Emperor') is divided into two parts. The first includes forty chapters with volvelles reproducing the position and the movement of celestial bodies, including the Sun, Moon, and planets. The second part describes the meteroscope, an instrument designed to solve problems in spherical trigonometry, and relates the sighting of five comets. 

The volvelles in the work are each placed within a frame reminiscent of an astrolabe, a contemporary device that modelled the movement of the Heavens in two dimensions and enabled the calculation of time and place and assisted with astrology. The first moveable woodcut, which represents the planispheric astrolabe, compresses both hemispheres onto one plate. According to the text, the plate depicts 1,033 stars, and was based on the first printed star charts published in 1515 by 

 and Johannes Stabius.

The most spectacular of the volvelles, which are the work of the artist Michael Ostendorfer (1490–1556), are the dragon plates. These include the title page and the double-page spread dragon and moon dials. The dragon dial can be used to calculate the nodes of the Moon, the two points of intersection between the yearly path of the Sun, and the plane of the lunar orbit, which produce eclipses. The thirteen small dragons indicate different parts of the lunar cycle. 

The work was produced in the family studio-workshop which was run by 

 and his brothers - they received a knighthood for their services. 

Binding: seventeenth-century full-mottled calf.

Collation: Folio. Titlepage framed by a woodcut border, on verso of the same leaf woodcut coat of arms of joint the dedicatees Charles V and his brother Ferdinand of Spain. Fifty-three eleven-line and thirty-nine six-line historiated woodcut initials by Hans Brosamer; thirty-six full-page woodcut astronomical figures coloured by a contemporary hand, of which twenty-one are volvelles (interactive wheel diagrams/instruments) with a total of eighty-three discs (complete); forty-four silk threads (complete); and twelve pearls (complete); full-page woodcut arms of the author by Michael Ostendorfer.

This pioneering textbook on astronomy was produced by 

, an astronomer and professor of mathematics at the celebrated University of Ingolstadt. It is dedicated to the Holy Roman Emperor Charles V (ruled 1519–1556) and his brother Ferdinand I. 

The works contains a comprehensive review of contemporary astronomical knowledge, conceptualising Ptolemaic astronomical theories. This book includes instructions on how to determine longitude using solar eclipses, how to calculate lunar eclipses, and the observation that the tails of comets always point away from the Sun. 

The work is beautifully illustrated and full of intricate working volvelles, hand-coloured in Apianus’s workshop. These interactive diagrams are tools used to calculate the positions of planets in the sky, eclipses, and even the hour of a baby’s conception. More than one hundred and twenty copies of this iconic work are known, and it was famously expensive in its day: even English astronomer and mathematician Edmund Halley could not obtain a copy, so King Henry VIII made, through his intermediary, a direct appeal to the printer to obtain a copy for the Royal Collection. 

This gorgeous edition preserves all of the silk threads and seed pearls used for reading the volvelles.

Apianus worked on this publication for eight years prior to its publication: the volvelles would have been cut, hand coloured and assembled with care in his family-run workshop. 

In dedicating his work to Holy Roman Emperor Charles V and his brother Ferdinand, the two ‘Caesars’ of the title, Apianus secured important patronage for his luxurious work of science. Throughout the work, his calculations are based on the birth dates of the brothers.

The second part of the work meticulously records Apianus's observations on the passage of five comets, including that which would later be named Halley's comet. He illustrates the phenomenon that comets' tails always trail away from the sun, a tantalising clue as to the heliocentric nature of the universe. In spite of this, Apianus's work describes a geocentric universe, just three years before Nicolaus Copernicus's revolutionary description of the true nature of our heliocentric Universe was published as 'De Revolutionibus' (1543). Apianus was probably aware of Copernicus's theories, however, his expanded development of the geocentric theory and Ptolemaic ideas in the ‘Astronomicum’ drew criticism from Johannes Kepler, who published a counter-argument in 'De Stella Nova' in 1606. 

Double volvelle spread

Frontispiece

Dedication page with coat of arms

Zodiac, Constellations

Volvelle

Saturn's orbit

Latitude of Saturn Volvelle

Jupiter's orbit

Jupiter Volvelle

Mars' orbit

Latitude of Mars Volvelle

Movement of the Sun

Movement of Venus

Latitude of Venus Volvelle

Mercury's orbit

Latitude of Mercury Volvelle

Volvelle with the zodiac 

Lunar volvelle

Volvelle to calculate when the moon reaches its apex

Lunar calculation volvelle

Moon volvelle

Volvelle for predicting lunar eclipses 

Eclipses of the sun and moon

Sun volvelle

Moon volvelle 2

Magnitude volvelle

Volvelle for planetary conjunctions

Volvelle for planetary conjunctions 2

Planetary movements volvelle

The Golden Number volvelle

Dominical letter volvelle

Calendar volvelle

Horoscope volvelle

Movement of the Moon in relation to the Sun

A pristine copy with distinguished provenance of 

 of the Emperor') – an important work to the history of science, astronomy, and computing. One of only about one hundred and thirty examples printed, each equipped with pearls and threads to aid calculation, and hand-coloured in Apianus's own workshop. 