A late 14th/early 15th century astrolabe attributable to the workshop of Jean Fusoris (1355-1456).

Brass, diameter 160mm.
The elegantly restrained rete carries flame-like pointers for 22 named stars. These are:



Engraved name                Identification
______________________________



Venter Ceti                         Zeta Cet
Cornu                                  Beta Arietis
Menkar                                Alpha Ceti
Aldebaren                           Alpha Tauri
Rigil                                     Beta Orionis
Alhaiot                                 Alpha Auriga
Algeuse                              Alpha Orionis
Alhabor                               Alpha Canis Majoris
Algomeisa                         Alpha Canis Minoris
Ydra                                     Alpha Hydra
Cor leonis                          Cor Leonis
Spica                                   Alpha Virginis
Eq[uus]                               Eta Ursa Majoris
Alrameth                             Alpha Bootis
Elfeta                                   Alpha Corona Borealis
Lansalibri                           Beta libre
Cor                                       Alpha Scorpio
Alhaue                                 Alpha Ophiuci
Wegua                                 Alpha Lyra
Althair                                   Alpha Aquila
Ariof                                      Alpoha Cygni
Humerus                             Beta Pegasi
___________________________________



The North-South and East-West bars are counter-changed. The Tropic of Cancer is depicted as a dragon and incorporates the pointer for Cor in its tail. The ecliptic circle carries the names of the signs but is undivided. Construction lines remain  on the reverse of the rete.



The small bracket for the suspension shackle and ring (both missing) is made in one piece with the limb. This is riveted to the back plate to form the mater which is plain except for six concentric circles and the ownership inscription 'PRO: MAGISTRO + PETRO + HILARETO + ANGERIACO + SANTONE + MEDICO + 1518' (For [or 'in the name of'] the master Peter Hilary of Indre, doctor at Saintes, 1518). At the centre is an emblem (perhaps heraldic) constituted by a bird holding a large worm or snake in its beak beneath a band with three ears of wheat. Several stress cracks resulting from the casting are to be seen in the brass. The limb itself carries  a 0-360° scale divided into groups of 5 each group of three being numbered 1 – 12 (x 2) for the 24 hours.



The back of the instrument is engraved on the outer edge with a degree scale numbered 90-0-90-0-90 by groups of ten. Within this is a zodiacal calendar (eccentric-type) with the signs and months named and the latter divided to days. There are some errors in the numbering, the 31 of March for example being cut over a 30, and the 28 of February over another number. Traces of black and red infill to the names and numbers remain. The centre upper half carries an unequal hour scale numbered 1-6-1, while in the lower half is a double shadow square of twelve numbered by groups of four. The value of  0° Aries, 11.5 March, is consistent with the date ascribable to the instrument on stylistic grounds.



There are four plates, engraved on each side, for :



Parisius         Paris           48g  50m         rome           Rome     41g 45
Poitiers          Poitiers       47                      lion              Lyon        45
rodis              Rhodes       35g 30m          tablet of horizon
hiers              Jerusalem  30g 45m          tron                               24



The locking lug is placed as an extension of the meridian line, the altitude lines are drawn for every 2°, the azimuths for every 10°. Arcs for unequal hours (numbered every two, 2 – 12) are drawn beneath the horizon line together with the name and latitude of the place for which the plate is drawn.



The instrument is completed by a counter-changed alidade, mounted on the back with chamfered and fringed edges and neatly effected openings at each end to allow the scale beneath to be read. The fixed vanes (inset and soldered) have pinnule and bar sights. On the face is a plain half rule (ostensor) with one chamfered and fringed edge and a lobed end.

Christie's South Kensington, 3 April 2005 lot 587.

Fausto Casi, 'Un astrolabio planisferico medievale della tradizione di Jean Fusoris', La Voce di Hora, xv 2003, 63-82.
Emmanuel Poulle, Un Constructeur d'instruments astronomiques au XVe siècle : Jean Fusoris, Paris 1963.

This neatly executed instrument belongs stylistically to group of late medieval astrolabes which are attributed to the workshop of Jean Fusoris on the basis of the close similarity to be found between their construction and that of the instrument described by Fusoris in his treatise on the astrolabe (see Poulle 7-19). The form of sighting vane used on the instruments is claimed by Fusoris to be original to him and all the astrolabes attributed to him incorporate an error in the placing of Cornu arietis, which is given a southern declination rather than a northern one, exactly as it is in Fusoris' written description of the instrument. Poulle in 1963 (pp.20-21) was able to identify some fifteen instruments from Fusoris' workshop since when a further  three have been found together with a number of derivative instruments (see the list given by Casi 78-79). The present astrolabe is unusual in incorporating the star lanca libre which occurs on only two other instruments (Poulle 23).

Jean Fusoris was born at Giraumont in the Ardennes, probably in 1365, the son of a pewterer. He studied at the University of Paris, obtaining the degrees of Master of Arts, of medicine and bachelor of theology. Ordained in 1411, he became a canon of Notre Dame, Paris, the same year and acquired other benefices. At a date unknown he began to make the mathematical instruments with which his studies would have familiarised him and was quickly successful acquiring as clients such notables as the Duke of Orléans, the King of Aragon, the King of Navarre and even the Pope. Inventive and innovative he extended his production to planetary instruments. One of these, sold to Robert de Courtenay, Bishop of Norwich in 1414, led inadvertently to his indictment for treason, to an inconclusive trial and perpetual exile to Mezières-sur-Meuse. Nine years later, however, he received a major order from the chapter of Bourges cathedral for an astronomical clock (still surviving it is the oldest complete clock in France). In 1432, the chapter of Metz  cathedral ordered a cosmographical treatise from him, and Charles VII the calculation of new astronomical and trigonometrical tables.  He died in 1436 leaving them incomplete.