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Astrolabe
Signed by Cornelius Vinch
Dated 1599; Naples
Brass; 201 mm in diameter

The rim of the mater bears an equal 24-hour scale and a 360? altitude scale. The equal hour scale is numbered twice from I to XII starting at the throne, divided to 20 minutes, subdivided to 4 minutes. The altitude scale is numbered anticlockwise by 10? starting at the west point, subdivided to 5? and subdivided to single degrees. The rim is soldered to the backplate. The inside of the rim has a recess at 12 o'clock underneath the throne to accommodate the tongues of the plates.

The inside of the mater is devoid of markings. The throne consists of two raised foliate scrolls with an inset swivel pin.

The rete has a complete equatorial circle ; the star pointers are worm-shaped. The names of 50 stars are given, mostly with their magnitudes and corresponding planetary temperaments.

The ecliptic is marked with the usual Latin names for the zodiacal signs and their symbols. Each sign is divided into 30? numbered by 10? divided into 5? and subdivided into single degrees.

The equator has a 360? scale starting at the first point of Aries anticlockwise, numbered by 10?, divided by 5? and subdivided into single degrees.

The four plates are marked on both sides with the circles for the equator (marked 'Aequinoctialis') and the tropics (marked 'Tropicus Cancer' or 'Cancri' and 'Tropicus Capricornus'), azimuths for every 5? (numbered by 5?), almucantars for every 5? (numbered by 5?), the lines for the unequal hours (numbered 1 to 12), markings for the astrological houses in the manner of Regiomontanus (numbered I to XII), the 'Horizon obliqus' and the 'HORIZON RECTUS' and the twilightcurve (marked 'LINAE [sic] AVRORE SIVE CREPVSCOLINE'). The sides are marked and laid out for the following latitudes ('Polus Graduum'): 1a) 35?; 1b) 38?; 2a) 42?; 2b) 45?; 3a) 431/2? ['Gradorum' instead of 'Graduum']; 3b) void except for the three main circles; 4a) 48?; 4b) 52?.

The back of the instrument bears several circular scales as follows (from the outside):

1) A concentric 360? altitude scale, marked four times 0? to 90? starting on the east-west line in both directions, numbered by 5?, subdivided to single degrees.

2) A concentric scale with the names of the zodiacal signs marked with the usual Latin names, their symbols and the corresponding planetary houses, each sign divided into 30?, marked by 5? and subdivided to single degrees.

3) An eccentric calendar scale marked with the usual Latin names of the months, divided into the corresponding number of days, every fifth day marked, with subdivisions into single days. The equinoxes correspond to March 21 and September 231/2. The bottom half of the vacant space inside these circles is taken up by a double shadow scale marked 'VMBRA VERSA' and 'VMBRA RECTA' to the base of 12 with divisions into 2 digits (every second numbered) and subdivisions into single digits and 0.2 digits. On the inside of the shadow scale is the signature 'CORNELIO VINCH FIAMENGO DE ANVERSA FECEB{AT} NEAPO{LIS} MDXCVIII'. The space outside the shadow square is filled with a floral design with strapwork and grotesque masques.

The top half contains a double horary quadrant for unequal hours, marked I to XII. Inside the midday circle is a wreath.

The rule, marked 'INDEX' on one arm, is counterchanged and marked with an irregular scale 65? to 0? to 25?, every 10? numbered, divided to 5? and subdivided to single degrees. There is no alidade.

The instrument was presented by A.W. Franks in 1857 and is described in F. A. B. Ward, A Catalogue of European Scientific Instruments in the Department of Medieval and Later Antiquities of the British Museum (London, 1981), p. 118, no. 340.

Silke Ackermann

British Museum, London
Registration no. MLA 1857,8-4.31

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