Giovanni Antonio Magini Planispheric Quadrant
Record status
Individual type · partial
Period
Late 16th century
This 297 mm radius brass quadrant, signed by Giovanni Antonio Magini, functions as a model of the heavens and a calculating device. It serves as a planisphere, incorporating a stereographic projection of the northern hemisphere on one side and a projection of the heavens on the other, functioning essentially as a folded astrolabe.
A radial rule, constructed from two soldered brass components, allows for the instrument's use on both sides. The device features highly complex engravings, including celestial latitude and longitude scales, ecliptic divisions, astrological houses, almucantars, and 31 named stars. Additional decorative elements include a coat-of-arms in the centre and geometric motifs along the edges. The instrument is equipped with a ring at its apex for suspension.
It is held in the collection of the Museum of the History of Science, Oxford.
Evidence at a glance
- Linked sources
- 1
- Photograph views
- 1
- Catalogue references
- 0
Counts describe this entry’s documentation, not authenticity, rarity or completeness. Photographs may show one specimen; check each caption and licence.
Technical characteristics
- Date
- Late 16th century
- Type
- Italian quadrant
- Maker
- Giovanni Antonio Magini
- Origin
- Italian
- Radius
- 297 mm
- Material
- Brass
- Star count
- 31
- Place recorded
- Italy
- Maker / attribution
- Giovanni Antonio Magini
Design
- Visible features
- • Radial rule constructed of two brass parts • Apex ring for suspension • Engraved coat-of-arms with a pyramid and two stars in the centre • Decorated edges with geometric motifs
- Inscriptions and Markings
- The instrument is explicitly signed by the maker, Giovanni Antonio Magini, on the edge of the quadrant. Various scales are numbered in complex, often bustrophedic arrangements to accommodate the geometry of the device. Specific lines, such as those for celestial latitude and declination, are marked with Latin inscriptions. At the central point of the instrument, a distinctive coat-of-arms is engraved, featuring a pyramid atop a rectangular base, positioned between two stars.
- Structural Design and Components
- The instrument is a large, brass-constructed quadrant with a radius of 297 mm, featuring a suspension ring at its apex. It incorporates a dual-sided radial rule, designed by soldering two separate brass components together, enabling its application across both faces of the instrument. The edges and limb are finished with geometric decorative motifs. This quadrant is identified as a functional model of the heavens rather than an observational tool. Its design is derived from 13th-century principles established by Profatius Judaeus, essentially functioning as a folded astrolabe capable of complex astronomical calculations.
- Celestial Projections and Engravings
- One face displays a polar projection of the celestial sphere with lines marking degrees, celestial latitude, and longitude. It includes an ecliptic divided into degrees with associated zodiacal symbols and astrological houses. The sliding rule here features unequal scales of latitude. The reverse side features a geocentric projection of the heavens. Engravings include the meridian, the horizon, equinoctial and tropic lines, and almucantars spaced every 3 degrees. Zodiacal signs and the names of 31 stars are present, alongside scales for right ascension and elevation.
Identification
- Inventory number
- 31514
- Source note
- Facts transcribed from the linked source listing or collection record. Attribution and specifications are source-reported and have not been independently authenticated.
Catalogue references
No catalogue numbers recorded. Numbers are only published once transcribed from a verified edition of a standard catalogue — they are never inferred.
Research required
- Research required: The source notes the instrument was 'probably' not used for observation
- Research required: It is uncertain if the full sequence of numbers is visible due to the sliding rule covering parts of the instrument