Astronomical Ring Dial
Record status
Individual type · partial
Period
Mid 16th century
This astronomical ring dial, currently held by the Museum of the History of Science in Oxford, is an 182 mm diameter brass instrument. Although the piece is unsigned, it is attributed to Johannes Motter, active in Louvain during the mid-16th century, based on comparative analysis with signed and attributed examples in Brussels and Florence.
The instrument conforms to the design described by Gemma Frisius, featuring folding meridian, equator, and declination rings, alongside a sliding inner ring equipped with sights. The dial is complex, incorporating latitude scales, polar distance quadrants, hour scales, shadow squares, and zodiacal calendars. Notably, the instrument includes the date '1602' engraved on the meridian ring; however, this marking appears in a style inconsistent with the rest of the object, suggesting it was added by a later owner long after the instrument's original construction.
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
- Mid 16th century
- Type
- Flemish astronomical ring dial
- Diameter
- 182 mm
- Added date
- 1602
- Provenance
- Lewis Evans Collection
- Attribution
- Johannes Motter
- Place recorded
- Louvain
- Maker / attribution
- Johannes Motter
Design
- Visible features
- • The instrument is constructed from brass. • It features folding meridian, equator, and declination rings. • The sliding inner ring is equipped with a pair of pinhole sights. • The meridian ring includes a scale for latitude from 0 to 90 degrees.
- Attribution and Dating
- The instrument remains unsigned, yet it is attributed to the Louvain instrument maker Johannes Motter. This conclusion stems from comparisons with a known signed instrument by Motter in Brussels and another unsigned example in Florence. Examination of the engraving indicates that the style of these specific numerals differs significantly from the rest of the instrument's inscriptions. The discrepancy in engraving technique supports the conclusion that the date was not inscribed by the original maker. It is therefore interpreted as a later addition by an owner rather than an indication of the instrument's initial creation. By disregarding this later mark, the constructional characteristics remain consistent with the mid-16th-century output associated with Motter's work in Louvain.
- Construction and Design
- The astronomical ring dial is a brass instrument measuring 182 mm in diameter. Its architecture consists of a folding meridian ring, an equatorial ring, and a declination ring. This configuration follows the specific form documented by Gemma Frisius. The meridian ring serves as the frame, featuring a latitude scale divided from 0 to 90 and a quadrant for polar distance. The suspension plate, which attaches to the meridian ring, contains slots specifically designed to facilitate fine adjustments to the latitude setting. The equatorial and declination rings are mounted within this structure, providing the primary mechanisms for solar timekeeping. The equatorial ring includes dual-faced hour scales, a shadow square, and a zodiacal calendar distributed across its outer and inner rims. The declination ring is similarly functional, carrying its own zodiacal and hour scales, and the outer rim is marked with the specific declination of twenty numbered stars to assist in celestial calculations.
- Functionality and Provenance
- The sliding inner ring, which is slotted into the declination ring, contains sights with pairs of pinholes. These allow the user to align the instrument with celestial bodies. The internal rim of this sliding ring is calibrated with a zodiac scale and positions for twenty specific stars. This allows the user to perform conversions between the right ascension of stars and solar time, providing a multi-functional approach to navigation and timekeeping. The instrument holds a documented history within the Lewis Evans Collection, which forms part of the holdings of the Museum of the History of Science in Oxford. The item is catalogued under inventory number 35171, representing its formal accession into the museum's collection of scientific instruments.
Identification
- Inventory number
- 35171
- 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 attribution to Johannes Motter is based on stylistic comparison rather than a signature.
- Research required: The '1602' date appears to be a later addition not reflective of the object's original manufacture date.