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Inventory no. 33871 - Epact entry

Epact number: 97152

Nocturnal and Sundial

Signed by Caspar Vopel
Dated 1557; Cologne
Brass; 130 mm in diameter

Main text

This instrument has the customary shape of a nocturnal, but in fact comprises several instruments. With one side the time can be discovered at night with a nocturnal, but some of the same scales are used in a volvelle for finding the age of the moon at any date. The other side has a Regiomontanus-type sundial for finding the time during the day.

A similar instrument is to be found in the British Museum, London (Epact 53179).

Source museum: Museum of the History of Science, Oxford
Museum number: Inventory no. 33,871

Detailed text

The nocturnal side has a zodiacal calendar on the base plate: the calendar scale is marked with the names of the months, divided to 10 and subdivided to 1 day, numbered by 10 (adjusted to the days in the month); the zodiac scale has the names and engraved representations of the constellations, and each sign has a scale 0 to 30 degrees, divided to 10, subdivided to 1, numbered by 10. There are two moving volvelle plates. The first has a pointer, marked 'INDEX SOLIS' and with a sun symbol, extending across the zodiacal calendar, and carries scales for the time and the age of the moon. The time scale had hours 1 to 12 twice, divided to 1, subdivided to 15 minutes, numbered by 1 hour, and each hour position between 8 to 1 and 11 to 4 has a point for counting in the dark (12 has the index arm). The lunar scale runs from 0 to 29|1/2|, divided to 1, subdivided to |1/4|, numbered by 1. The inner moving plate has a pointer, marked 'INDEX LVNAE ET ASPECTVVM PLAN.' and with a moon symbol, and is engraved with a diagram of planetary aspects marked 'PLANETARVM ASPECTVS'. It is pierced to reveal on the first moveable representations of lunar phases and parts of inscriptions. A long central index arm extends beyond the limit of the base plate; around the central pivot is engraved, 'STELLA POLARIS IN CAVDA VRSAE MINORIS'; the tip of the arm is marked, 'INDEX HORAR PLAVST VRSRA MAIOR', and with a diagram of the constellation; engraved along the length of the arm is, 'DVAE PARITES PLAVSTRI POSTREMAE A STELLA POLARI CYNOSVRAE IN RECTAM DVCTAE SOLIS INDICE AD DIEM MENSIS OBLATVM POSITIO HORAM OSTENDVNT NOCTVRNAM'. The assembly is held together by a rivet with a central hole for viewing the pole star.


The sundial side has a Regiomontanus-type altitude dial with pinhole sight vanes and a three-element articulated arm for adjusting the point of suspension of the plumb-line (weight missing) on the triangular grid of latitude and zodiacal position. The zodiacal symbols are at the top, with each sign divided by three; the latitude scale is from 0 to 65, divided to 5, 5 to 65 subdivided to 1, numbered by 5. The grid is marked on one side, 'ZODIACI LATITVDINVM SCALA', and on the other 'ZODIACI LATITVDINVM QUAE ET POLI ELEVATIO SIVE BOREI SIVE NOCTII'. The hour lines are numbered both [0] to 12, 'HORAE ANTE MERIDIANAE', and 12 to 1, 'HORAE POMERIDIANAE'. There is a solar declination scale to the right of the hour lines, marked with zodiac symbols, this scale and the mid-day hour line being marked 'GENERALIS ZODIACVS ET MERIDIANVS'. The midnight line is marked 'MEDIVM NOCTIS SEPTENTRIO'.

Around the edge of the sundial side are two altitude scales to be used with the sights and the suspension point set to a position marked 'CENTRVM QVADRAN'. The outer is a scale of degrees radiating from this point, 0 to 90, divided to 5, subdivided to 1, numbered by 5, marked 'QVADRANS ASTRONOMICVS'. The inner is a geometrical quadrant or shadow-square scale, 0 to 60 to 0, divided to 5, subdivided to 1, numbered by 5, marked, 'QVADRANS GEOMETRICVS' and 'VMBRA VERSA' and 'VMBRA RECTA'.


The handle on this side has a crest with three crowns and is engraved, 'HOROMETRI FACIES AD OMNEM REGIONVM LATITVDINEM TAM BOREALEM QVAM AVSTRINAM CON SCRIPTA'.

Jim Bennett

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