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Inventory no. 55203 - Epact entry

Epact number: 11158

Nocturnal and Quadrant

Dated 1543; French
Brass; 71 mm in diameter

Main text

This is a small instrument but it offers many different functions.

The nocturnal side, besides telling the time at night from the position of the stars, has a volvelle for predicting the age or phase of the moon. The reverse has two types of horary quadrant, a shadow square and a degree quadrant, all squeezed onto a small disk with their lines overlapping.

Source museum: Museum of the History of Science, Oxford
Museum number: Inventory no. 55,203

Detailed text

The nocturnal side has a zodiac scale with the names of the constellations, each constellation divided to |1/6|, subdivided to |1/30|, not numbered, and an inner scale is divided 1 to 28. A moveable volvelle disc has an index arm extending across the zodiac scale and carries an hour scale divided 1 to 12 twice, the night hours being indicated also by points, and a scale for the age of the moon, divided 1 to 20. A second moveable disc, marked with the signs of the Ptolemaic planets, has an index arm for the nocturnal function and a circular aperture revealing the phase of the moon.

The quadrant side has a pair of pinhole sights and a plumb-line with a weight (bead missing). Quadrant scale 0 to 90, divided to 5, subdivided to 1, numbered by 10, and a shadow square 0 to 12 to 0, divided to 3 subdivided to 1, numbered by 3, the sides marked 'VMBRE DR|OI|CT' and 'VMBRE VERSE'. The quadrant scale enclosed the unequal-hour lines of the quadrans vetus, numbered 12, 11 / 1, 10 / 2, 9 / 3, 8 / 4, 7 / 5, 6 (noon), and outside the quadrant a zodiac scale with the names of the signs, each divided to |1/6|. There is a second set of hour lines for ordinary hours, 4 / 8, 5 / 7, 6 / 6, 7 / 5, 8 / 4, 9 / 3, 10 / 2, 11 / 1, 12 (noon), used in conjunction with a solar declination scale on the right of the hour-lines, marked with signs of the zodiac. There is a second zodiac scale. The sunrise/sunset line is marked, 'LORIZON DE SOLEIL LEVANT'. There are three engraved scrolls; two are blank, one has the date '1543'.

Jim Ben nett

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