This article discusses three aspects of the history of astrology in seventeenth-century Peru that are of larger interest for the history of science in Latin America: Creole concerns about indigenous idolatry, the impact of the Inquisition on natural philosophy, and communication between scholars within the Spanish colonies and the transatlantic world. Drawing mainly on the scholars Antonio de la Calancha, Juan de Figueroa, and Ruiz de Lozano, along with several Jesuits, the article analyzes how natural and medical astrology took shape in Peru and how they fostered astronomical investigations of the southern skies. While natural and medical astrology, showing New and Old World influences, oscillated between orthodoxy and heterodoxy, and between scholasticism and new science, judicial astrology remained undeveloped. Toward the end of the seventeenth century the discourse about astrology took an unexpected turn, reflecting a newly invigorated moral and Christian reading of the heavens that was in part a response to a deep-rooted dissatisfaction with the failure of the extirpation of idolatry campaigns. Inscribing divine and cardinal virtues, the Virgin Mary, Christian saints, and Greco-Roman allegories into the heavens was considered a way to finally solve the problem of idolatry and to convey Creole greatness.