Astronomical Compendium by Tobias Volckmer

Technical characteristics

Date

1584

Type

German astronomical compendium

Maker

Tobias Volckmer

Material

Gilt brass

Signature

THOBIAS VOLCKMER BRAVNSWEIGSENSIS FACIEBAT ANN CX 1584

Components

Two shadow squares, horizontal sundial, compass, nocturnal and quadrant

Dimensions

70 x 70 x 17 mm

Place recorded

Germany

Maker / attribution

Tobias Volckmer

Design

Visible features

• The object is constructed of gilt brass with exterior strapwork and wreath decoration. • The interior features a central circular compass housing with a silvered base plate. • A folding gnomon is present on the dial but is noted to be potentially a later replacement. • The instrument uses punched letters and numerals for its various scales.

Construction and Design

The compendium is built around a central box that houses a removable compass unit. The box is equipped with front and back covers hinged on opposite sides, allowing the instrument to fold into a compact form measuring 70 x 70 x 17 mm. The decorative treatment on the exterior includes strapwork and wreaths along the sides, while fruit motifs occupy the corners. Internally, most markings are executed by punching rather than engraving. The front cover functions as a horizontal sundial and includes a shadow square marked with 'VM. RECT.' and 'VM. VER.' elements. It is fitted with a folding brass gnomon. The dial surface is marked with circular hour scales for latitudes 45, 48, and 51. The design also incorporates supporting struts to hold the cover open during use, and the entire assembly features a slight deviation, with north inclined westwards.

Compass and Nocturnal Functions

The central compass component consists of a bowl featuring a silvered base plate with an engraved needle indicator, though the needle and glass cover are no longer present. This unit is secured in the box by two retaining clasps and can be removed. The bowl rotates within a surrounding disc that carries a circular scale of compass directions indicated in German. An hour ring from 1 to 24 is also present, and the disc is mounted with six studs to facilitate rotation. The inside of the back cover houses a nocturnal with a lunar volvelle. This mechanism is calibrated for a star sharing the sun's right ascension on approximately 20 August. The nocturnal plate includes a calendar scale, moon age indicators, and a lunar phase aperture. The volvelle itself provides dual time-telling scales, although the index arm required for the nocturnal function is currently lost.

Additional Astronomical Features

Beyond its primary dial and nocturnal functions, the instrument incorporates a quadrant on the back cover, marked with a scale of 0 to 90 degrees. This quadrant includes its own integrated shadow square labeled 'VMBRA RECTA' and 'VMBRA VERSA' with a central square grid. A small hole located at the vertex indicates the former presence of a plumb bob. Three of the four sides of the internal layout feature a scale of equal parts. Additionally, the back cover contains an empty shield intended for a coat of arms, though it remains unpopulated. The instrument's identity as an early piece by Tobias Volckmer is established by the signature located within the shadow square on the front cover, which includes his place of origin and the date of manufacture.

Identification

Inventory number

34940

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.