Nocturnal and Regiomontanus-type sundial

Technical characteristics

Date

1557

Type

German nocturnal and sundial

Maker

Caspar Vopel

Diameter

130 mm

Material

Brass

Place recorded

Cologne

Maker / attribution

Caspar Vopel

Sundial side inscription

Signature of maker

Nocturnal side inscription

Engraved along the nocturnal arm

Design

Visible features

• Nocturnal side features engraved zodiac signs and month names on the base plate. • Sundial side includes a three-element articulated arm and a triangular grid. • Central index arm on the nocturnal side is marked for alignment with the constellation Ursa Major. • Peripheral scales include an astronomical quadrant and a geometrical quadrant on the sundial side.

Construction and Design

The instrument is a brass disc, 130 mm in diameter, comprising two distinct timekeeping faces. The primary assembly is held together by a central rivet that functions as an aperture for sighting the pole star. The nocturnal side is organized around a base plate containing a zodiacal calendar, which includes both the names of the months and engraved representations of the constellations. Two moving volvelle plates are mounted here, the outer carrying an index marked 'INDEX SOLIS' and the inner containing a lunar aspect diagram. The sundial face is a Regiomontanus-type altitude dial. It is equipped with pinhole sight vanes and a three-element articulated arm designed to adjust the suspension point of a plumb-line, which is now missing. The dial face is complex, featuring a triangular grid for latitude and zodiacal position, multiple hour scales, and a solar declination scale.

Engravings and Markings

The instrument is densely engraved with Latin inscriptions, scales, and diagrams that facilitate its use. The nocturnal side contains hour markings on a time scale with points for dark-counting, as well as a lunar scale ranging from 0 to 29.5. The long central index arm, used for night time calculation, features an engraved diagram of Ursa Major and detailed instructions on its usage. On the sundial side, the engraving includes designations for morning and afternoon hours, as well as specific markings for the midnight line and solar declination. The periphery of the disc hosts two distinct altitude scales: one for astronomical measurement and one for geometrical or shadow-square calculations. The maker's signature is located on the sundial face, specifying the location of Cologne and the year 1557.

Provenance and Research

The object is held in the collection of the Museum of the History of Science, Oxford, and assigned the inventory number 33871. Records indicate that a similar instrument, serving as a comparative reference, is held in the collection of the British Museum in London. The object's functionality relies on the use of both side-mounted handles, one of which includes a crest with three crowns and an inscription describing the instrument's capability to function at varying latitudes.

Identification

Inventory number

33871

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.