From his birth in 1459, when his mother had his horoscope cast by the renowned mathematician Regiomontanus, astrology played an important part in the life of the future Holy Roman Emperor Maximilian I. As Darin Hayton shows in The Crown and the Cosmos, Maximilian came to master the use of the celestial art for self-presentation and political ends, for decision making and shaping public opinion. Having learned astrology himself, as he advertised freely, he oversaw a programme to revitalize the University of Vienna that included the appointment of expert practitioners, whose work would become embroiled in matters of state. Astrology had long found a place at European courts, but Hayton argues that Maximilian did something new in his consistent and very public use of it to advance the Habsburg political agenda.

The narrative begins with Maximilian's self-fashioning as the ideal ‘modern’ prince, with autobiographical works presenting him as preordained to rule and well placed to take advantage of the celestial art through his own instruction in it and his use of skilled astrologers to guide his actions. The predictive and explanatory knowledge that astrology offered became central to Maximilian's courtly politics as he came to power, with the published predictions of astrological practitioners including Sebastian Brant and Joseph Grünpeck aligning with the emperor's goals and showing how his life was blessed through the stars as part of a divine plan.

Maximilian relied above all on the University of Vienna to supply astrologers skilled in an art that required rigour, accuracy and precision. Some came to work for him through official court appointments; others gave advice and intellectual support, becoming increasingly engaged in political matters over the course of Maximilian's reign. This continued at the court of Archduke Ferdinand, who ruled the Austrian hereditary lands after Maximilian's death in 1519 and became Holy Roman Emperor in 1558. The book covers a longer time frame than its title suggests.

Hayton then discusses the tools of astrology and how they came to be bound up with Maximilian's agenda. Astrological instruments featured as practical tools and as vehicles for propaganda. They embodied knowledge, and were used for making judgements and projecting political power. Maximilian also encouraged the dissemination of his political message through popular texts such as wall calendars, annual prognostications, almanacs, ephemerides and treatises on comets and conjunctions. These reflected contemporary fears over possible Ottoman invasion, the plague and other concerns, and offered predictions as to their likely occurrence and effects. Again, authors such as Georg Tannstetter and Andreas Perlach continued these activities after Maximilian's death. With many authors writing that a major set of planetary conjunctions in 1524 heralded a catastrophic flood, for instance, Tannstetter's prognostications reassured readers in Ferdinand's territories that all would be well. The right predictions might calm the masses.

The book concludes by asserting that Maximilian's legacy was for astrology to take on a similar role at other and later European courts. In Hayton's words, ‘Maximilian's efforts to establish patronage networks that linked individual experts as well as institutions to the court emerged as a central characteristic of early modern Europe’ (p. 13). Even at the end of the sixteenth century, Maximilian's self-presentation as skilled practitioner and generous patron of the sciences was echoed in the strategies adopted by Emperor Rudolf II.

One of the strengths of the book is its practical bent: we learn what university astrologers and their students were actually doing in the early sixteenth century and how their patrons were able to exploit this work. In part, this is a book about academics writing texts, but it is also about how those texts were tailored for political ends and used in different walks of life. Astrology, Hayton emphasizes, needs to be seen as ‘an integral facet of premodern politics’ (p. 9), a point that flags up interesting parallels with other recent work including Monica Azzolini's The Duke and the Stars: Astrology and Politics in Renaissance Milan (2013). Indeed, comparison with Azzolini's analysis of the Sforza dynasty might call into question Hayton's claim that Maximilian was absolutely the first to use astrology in an overtly political way.

If I were to ask for more, it might be to expand some of the contextual elements. There is some reference to the other strategies at play – the use of prophecy, history and genealogy as propaganda, for example, not to mention the visual arts – but it would be good to learn a little more about the full political context and deployment of these. I would really like to know how much effort was put into, and how much weight granted to, astrological in comparison with other strategies deployed within Habsburg courtly and political life.

Nevertheless, it is particularly illuminating to see the ways in which natural philosophy was treated by the Habsburg rulers as a practical tool with tangible outcomes. We learn of instruments and texts being created and used, of judgements being made and acted upon, for personal (often medical) and political ends, helping Maximilian decide when to arrive at negotiations or sign treaties. Adding to an expanding narrative of the role of astrology in Renaissance culture, this book further helps us to understand some of the practical ways in which natural philosophy operated within the political sphere in this period.