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Instrument type

circa 1450; French
Brass; 280 mm in diameter

The mater is made of two brass layers soldered together. It has no plates, therefore the mater itself is engraved. The limb is divided into 360? by 5? and by 1?, numbered 1 to 12 twice, every hour or 15?.

The inner side of the mater is engraved with '40', complement of the latitude 50? for which the astrolabe is made, with east-west and meridian line, both tropics and equator lines, azimuth, twilight and unequal hour lines engraved though not marked. There are 90 almucantars, engraved every degree. An inscription in the centre reads 'Jeh Charla'. A very faint engraving next to the tropic of cancer line reads '64'.

Suspension is by means of a ring, saddle-shaped shackle and small three-lobed throne.

The rete is boldly engraved: the ecliptic is divided on the edge into 360? by 30?, with further divisions to 5? and to 1?, with the zodiac signs' names engraved. It is connected with two ties to the Capricorn band. The east-west line is counterchanged twice and ends with semi-quatrefoil bearing star pointers. The meridian bar is also counterchanged, with a lobe bearing a star pointer, and ending at the bottom with a semi-quatrefoil with lead filling. There is a band, similar to the equinoctial, within the ecliptic circle. The star pointers, lambent, are for 37 stars all named in Lombardic script.

The back of the mater has a scale of degrees, divided by 30? with further divisions by 5? and by 1? but not numbered, with zodiac signs named, and a calendar scale closer to the centre, divided into 365 days (not numbered) with the names of the months indicated. For each month is indicated the dominical letter. The first point of Aries is the 11th of March. The centre of the plate is engraved with a double shadow square on the bottom half, numbered by 3, unequal hour lines superimposed on the left-hand quadrants, and equal hour lines, not numbered. The top left quadrant is left blank.

The rule is counterchanged and is engraved on one of the arms with an unequal scale of declination [0] to 20 in one direction and [0] to 75 in the other, with 'A' and 'B' engraved at the two ends. Both arms have a Gothic-style end.

The alidade is counterchanged and has a linear decoration, on both arms and on the centre, where dominical letters are also engraved. Its ends are in a Gothic style. The vanes have two sighting holes each.

The pin is decorated and the wedge is simple and symmetrical.

See R. T. Gunther, The Astrolabes of the World (2 vols, Oxford, 1932), vol. 2, p.309.

Ilaria Meliconi

Museum of the History of Science, Oxford
Inventory number 47674

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