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Treasures of the RAS

The Library and Archives of the Royal Astronomical Society contain books, images and documents significant in the development of scientific thought in astronomy, geophysics and related disciplines. In this series of articles and videos RAS Librarians display some of the gems of the collection.

Treasures of the RAS: Astronomicum Caesareum

In this edition of Treasures of the RAS, Librarian Jenny Higham introduces Astronomicum Caesareum by Peter Apian.

This gorgeously coloured book was published in 1540. This book was produced for Charles V, Holy Roman Emperor, and only a few were printed and then coloured by hand. It contains many elaborate moving paper discs, which can be used as instruments to calculate the positions of the planets.

The calculations were on the geocentric system of Ptolemy, who assumed that the planets, moon and Sun all orbited the Earth. A few years later Copernicus proposed the heliocentric theory, which made Ptolemy's system obsolete.

The Latin title is Astronomicum Caesareum (sometimes given as Caesarium), which translates as The Astronomy of the Caesars (Emperors).

Treasures of the RAS: Starry Messenger by Galileo Galilei

In this edition of Treasures of the RAS, Librarian Jenny Higham introduces Starry Messenger by Galileo Galilei.

In 1610 Galileo published this book describing his observations of the sky with a new invention - the telescope. In it he describes his discovery of the moons of Jupiter, of stars too faint to be seen by the naked eye, and of mountains on the Moon.

This book was the first scientific publication to be based on data from a telescope. It was an important step towards our modern understanding of the solar system.

The Latin title is Sidereus Nuncius, which translates as Starry Messenger or Sidereal Message.