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The Encyclopedia of Horology

Tool · German astronomical compendium

Astronomical Compendium by Tobias Volckmer

Partially verified

This astronomical compendium, measuring 70 x 70 x 17 mm and crafted from gilt brass, is signed by Tobias Volckmer and dated 1584. The instrument is constructed as a central box housing a compass, with two hinged covers. The front cover features a shadow square, a degree scale, and a horizontal sundial with a folding gnomon. The interior contains a removable compass bowl with a silvered base, and a rotating disc displaying compass directions and an hour ring. The back cover integrates a nocturnal with a lunar volvelle for tracking lunar phases and time, alongside a quadrant and an additional shadow square. Decoration includes punched letters and numbers, with side panels featuring strapwork and wreaths. The instrument currently exhibits several losses, including the compass needle, glass, nocturnal index arm, and a plumb bob.

The astronomical compendium shown open, revealing the internal dial scales, the compass housing, and the folding gnomon.
The astronomical compendium shown open, revealing the internal dial scales, the compass housing, and the folding gnomon. — Museum of the History of Science, Oxford. Rights pending — permission not yet requested. Original source

Catalogue identity

Source
www.mhs.ox.ac.uk
Category
Tool · German astronomical compendium
Maker / attribution
Tobias Volckmer
Reference
Not recorded
Catalogue / lot identifier
34940
Source-reported date
1584
Source-reported place
Germany

Source-reported attribution and specifications are not independent authentication. A listing does not establish present ownership, current display, availability or permission to reproduce.

Object description

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.

Evidence for this section
  • “The compendium consists of a central box for the compass with front and back covers.”
  • “The decorative scheme uses fruit in corners and free space, though the sides have strapwork and bound wreaths.”
  • “The whole dial is twisted slightly so that north is 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.

Evidence for this section
  • “The bowl has a silvered base plate with engraved needle indicator; the needle itself and the glass are missing.”
  • “On the inside of the back cover is a nocturnal with lunar volvelle.”
  • “The folding portion of the nocturnal's index arm is now 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.

Evidence for this section
  • “Inscribed within the quadrant is a shadow square, its sides marked 0 to 12 'VMBRA RECTA' and 'VMBRA VERSA'”
  • “The instrument is signed within the shadow square: 'THOBIAS VOLCKMER BRAVNSWEIGSENSIS FACIEBAT ANN CX 1584'.”

Open research questions

  • What is the purpose of the small stud found at the 1 o'clock position on the outer hour scale?
  • How did the presence of the now-lost plumb bob and alidade affect the original accuracy of the instrument's measurements?

Source evidence

Recorded claims and source quotations for Astronomical Compendium by Tobias Volckmer
FieldSource-reported valueSource quotation
MakerTobias Volckmer“Signed by Tobias Volckmer”
Date1584“Dated 1584; Brunswick”
MaterialGilt brass“Gilt brass; 70 x 70 x 17 mm”
Dimensions70 x 70 x 17 mm“70 x 70 x 17 mm”
Inventory number34940“Inventory number: 34940”
SignatureTHOBIAS VOLCKMER BRAVNSWEIGSENSIS FACIEBAT ANN CX 1584“'THOBIAS VOLCKMER BRAVNSWEIGSENSIS FACIEBAT ANN CX 1584'”
ComponentsTwo shadow squares, horizontal sundial, compass, nocturnal and quadrant“This device includes two shadow squares , a horizontal sundial , compass , nocturnal and quadrant .”

Visible details

  • 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.

Research qualifications

  • The source notes the gnomon may be a later replacement.
  • Several components including the compass needle, glass, and plumb bob are currently missing from the instrument.

Photograph identity and source facts were screened before import; rights clearance remains pending.

Consulted source

Astronomical Compendium

Reviewed 2026-10-26 · Record b92edc3c60

Terms in this record

Glossary explanations for terms named in this object’s record.

Other german astronomical compendium records