Medieval Astrolabe Quadrant
Record status
Individual type · partial
Period
Undated
This brass astrolabe quadrant, measuring 136 mm in radius, is one of seven such instruments recorded from the medieval period. It features a design that combines the functionalities of an astrolabe with those of a quadrant.
The instrument is unsigned, with an unknown origin, and remains undated. The brass plate has side lengths of 135 mm and 136 mm, with two fixed sights on one side and a hole indicating the former position of a plumb bob. The front contains complex scales for sines, cosines, declination, latitude, zodiacal signs, and unequal hour lines, alongside a shadow square and the positions of twelve identified stars. On the back, the instrument features two volvelles with indices, accompanied by zodiacal, Julian calendar, and solar cycle scales.
The lunar volvelle is unfinished, rendering its associated calendrical scales non-functional.
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
- Type
- Quadrant
- Material
- Brass
- Dimensions
- 136 mm radius
- Provenance
- Purchased from Christie's in 1995
- Star markings
- Twelve stars indicated
Design
- Visible features
- • Features two fixed sights located on one side of the brass frame. • Engraved with twelve specific star names, including 'Alchimek', 'Aldira', and 'Wega'. • Equipped with a shadow square to the base 12 on the front face. • Includes two volvelles with indices on the reverse side.
- Construction and Design
- The quadrant is constructed from a brass plate measuring 136 mm in radius, with side lengths of 135 mm and 136 mm. Two sights are fixed to one side of the instrument, and a hole is present where a plumb bob was formerly attached. The surface displays various astronomical markings, including a shadow square with a base of 12, unequal hour lines, and two arcs depicting the ecliptic, which are divided into the 12 signs of the zodiac. The front face contains detailed linear and circular scales. On the right-hand side, scales serve to determine sine and cosine values, while the left-hand side includes scales for declination and latitude. A double scale on the circular border provides 360 degrees of measurement. The engraving is described as lacking precision, and the lunar volvelle on the reverse remains unfinished, which prevents the use of the calendrical scales on the back.
- Astronomical and Calendrical Features
- The instrument incorporates diverse data for astronomical calculation. The front face lists twelve stars by name, including Alchimek, Aldira, and Wega. The zodiacal signs are represented through a dedicated scale and the ecliptic arcs. Several horizon lines are present, though the specific latitudes are not labelled. The back of the quadrant features two volvelles, each equipped with an index. These are associated with three circular scales: a zodiacal scale, a Julian calendar scale, and a solar cycle scale numbered 1 to 28. The first point of Aries is marked, though the divisions are noted as not being clearly defined.
- Historical Context and Identification
- This object is catalogued as one of only seven medieval astrolabe quadrants currently recorded. The design has been associated by some with Profatius (1236?-1305), although it is noted that features found on the instrument were also present on earlier Islamic devices. The quadrant was purchased from Christie's in 1995 and is sometimes referred to as 'PCII' in academic literature, such as in the work of E. Dekker. The instrument is currently held by the British Museum in London under the registration number MLA 1995,4-3.1. It is currently undated, and the origin remains unknown, despite its role in scientific and educational research as a representative of medieval instrument-making techniques.
Identification
- Reference
- PCII
- Inventory number
- MLA 1995,4-3.1
- 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 provenance and specific date of manufacture remain unknown, though some research associates it with the approximate period of c. 1300.
- Research required: The attribution of the instrument's design to Profatius is noted as a general historical perspective rather than a confirmed fact.