The Important Regiomontanus/Cardinal Bessarion Astrolabe, dated 1462

The Important Regiomontanus/Cardinal Bessarion Astrolabe, dated 1462,
CCA 640,
A brass European astrolabe inscribed on the back plate 'SVB DIVI BESSARIONIS DE CARDINE DICTI/PRAESIDIO ROMAE SVRGO IOANNIS OPVS 1462' (Under the protection of the divine Bessarion on whom all can be said to depend I arise [appear/come forth] in Rome the work of John 1462).

Rete
The restrained tracery, composed of flat curves symmetrically disposed around a semi-quatrefoil placed beneath the ecliptic circle, carries lightly curved pointers arising from open ring bases for thirty named stars. The Capricorn ring ends in two leaf-forms worked in relief; there is no Capricorn pointer. The stars marked are:

Stars outside the ecliptic
CAVDA CETI - Cauda ceti - β Ceti
VENT CETI - Venter ceti - ζ Ceti
NAR CETI - Naris ceti - α Ceti
OCVL TAV - Oculus tauri - α Tauri
PES DEX OR - Pes dexter Orionis - β Orionis
CAN MA - Canis major - α Canis Maioris
CAN MI - Canis minor - α Canis Minor
YDRA - Hydra - α Hydræ
COR LE - Cor leonis - α Leonis
VAS - Vas aquarium - α Crateris
SPICA - Spica virginis - α Virginis
CORVVS - Corvus - γ Corvi

Stars inside the ecliptic
CAV VR - Cauda ursæ - η Ursæ Majoris
CAV LE - Cauda leonis - β Leonis
HIR AG - Hircus aurigæ - α Aurigæ
CA DR - Caput draconis - γ Draconis
VVL CA - Vultur cadens - α Lyræ
GAL - Gallina - α Cygni
MV EQ - Musita equi - ε Pegasi
CAP GOR - Caput Gorgoni - β Persei
HV EQ - Humerus equi - α Pegasi
CRVS PEG - Crus pegasi - β Pegasi
MAN SER - Manus serpentarii - δ Ophiuchi
HER - Hercules - α Hercules
CAP SER - Caput serpentarii - α Ophiuchi
VVL VOL - Vultur volans - α Aquiliæ
DELPH - Cauda delphini - ε Delplini
BOET - Boetes - α Boetes
CORONA - Corona - α Corona borealis
VM AND - Umbilicus Andromdæ - β Andromedæ

Limb
Since a recess was required on each face of the instrument, the limb is constructed of two parts each integral with the throne, rivetted to the mater, and held tightly together either by rivets, perhaps by solder.

On the face, the limb carries only a degree scale, divided to single degrees by groups of five, and numbered every ten. At an indeterminable later date, perhaps during the 16th century, the outer edge was engraved with numbers for the hours.

The mater is provided by a single flat-filed plate probably from a hammered sheet derived from a cast slab. It is blank on both faces although traces of some casting fissures can be seen.

Throne
This is composed of a triangle formed from three roundels each decorated on the face with five concave circles set around a central boss to give a petal of almost clover-like appearance. On the back the two lower roundels carry six-pointed stars while the upper roundel has petal decoration similar to that on the front. The triangle is supported by scrolled-over leaf-heads, similar to those that terminate the Capricorn circle. A shackle with a cross-shaped head straddles the upper roundel and carries a swivel ring.

Back
On the edge, the limb is engraved with a degree scale in four quadrants 90-0-90-0-90° to allow readings to be taken in both altitude and zenith distance. Each quadrant is divided to 1° and numbered by groups of 10°. The reading direction for the numerals, i.e. from the outer edge towards the centre or from the centre towards the edge, is reversed in each quadrant. Within this is a zodiacal calendar (0° Aries = 10.75 March), the months divided into individual days with the idiosyncrasy that the first two letters of the name of each sign and each month are placed at the end of their division rather than at the beginning thus, for the signs, replacing 30, and for the months replacing 28, 30, or 31. For February however the final 3-day space was too small leading 'FE' to be engraved in the previous 5-day space. A final scale at the centre, concentric with all the others, is in fact two. The upper semi-circle is divided to degrees 0-90-0; the lower semi-circle is divided 0-12-0 by single divisions numbered every two, and thus serves as a shadow square for height and distance operations. Inset in the cavity produced by the limb being proud of the mater, and free to rotate, is a disc engraved across its centre with an orthographic projection known as an organum Ptolemei (a device for reckoning time in equal hours from the solar altitude), sustained by a clothed winged figure (? an archangel), with the inscription explaining the origin of the instrument below.

Plates
The three plates are drawn for
39°/54°
42°/51°
45°/48°
with that for 42° being specifically marked for the latitude of Rome. That they are engraved in a running series of 3° divisions on the separate plates rather than recto/verso (ie 39°/42°) is relatively unusual.

Each plate has an upper, unperforated, locating lug, is engraved with the usual almucantars (circles of equal altitudes above the horizon) and azimuths at 5° intervals, the tropics, the crepuscular line, and lines for the unequal hours numbered 1-12 beneath. The 48° plate is additionally engraved with lines for the astrological houses of the heavens.

Rule
The double-arm rule is engraved with a declination scale allowing the angular distance of a celestial object from the celestial equator to be determined.

Alidade horse and pin
None of these are likely to be original to the instrument. The plain cast alidade has lost the vanes once hinged to its extremities and has been cut down to coincide with the edge of the instrument, thus losing it points. The chemical composition of its brass however, as that of the pin, is similar to that of the rete. Turner (p. 2) in 1989, already noted that the wedge (horse) had been lost and been fitted with a replacement. ICC N° 640.

Sold with this lot is a copy of the publication by David A King: Astrolabes and Angels, Epigrams and Enigmas: From Regiomontanus' Acrostic for Cardinal Bessarion to Piero della Francesca's Flagellation of Christ, 2007
5 1/3in x 4 1/2in x 1 1/2in (135mm x 115mm x 40mm)
Exhibited
'Bessarione e l'Umanesimo'. Exhibition in the Biblioteca Nazionale Marciana 27 April- 31 May 1991.

Provenance
According to family tradition presented to William (1771-1860) and Mary Somerville (1780-1872) in Rome in March 1848 and by them given, at an unknown date, to John Herschel (1792-1871) the dedicatee of Mary Somerville's book Physical Geography, 29 February 1848, he having been her mentor and 'my dear friend for many years' as she described him in her Personal Recollections.

Sir John Herschel's executors in 1871 were his widow and the Manchester businessman and MP, Edward Hardcastle (1826-1905). His son, Henry Hardcastle (1840-1922), a barrister, had married Sir John Herschel's daughter Maria Sophia Herschel (1839-1929), while Sir John's own son, William James Herschel (1833-1917), had married Anna Emma Hardcastle. It was presumably through this close familial connection that the astrolabe passed into the possession of the Hardcastle family where it remained until late 1956 when it was lent by Commander M. H. Hardcastle to Derek J. de Solla Price (19822-1983) who employed it during a lecture tour in the United States. In October 1958 it was placed on extended loan to the National Maritime Museum, Greenwich whence it was withdrawn in 1985 to be sold at Christie's South Kensington on 28 September 1989.

The protagonists
The attribution of this instrument, signed only 'John' depends on the interpretation of the inscription. From this it seems clear that it was produced as a result of patronage from the Cardinal Bessarion.
Johannes Bessarion (between 1399 and 1408 - 1472) entered the order of St Basil at an early age studying letters and philosophy in Constantinople and Mistra (1416-36). Raised to the bishopric of Nicæa (1437), he was sent by John Palæologus to the Council of Ferrara-Florence charged to discuss the reuniting of the Greek and Roman churches (1437-39). Here he distinguished himself by his eloquence in the cause of such a unification and was created a Cardinal-priest by Pope Eugenius IV in 1439. Subsequently, after he had settled in Italy, he would become Archbishop of Sabina, cardinal-bishop, and be named Patriarch of Constantinople in 1463. Much employed on papal diplomatic missions, Bessarion was a fully-fledged humanist scholar to whom several translations from Greek into Latin are due, an ardent Platonist, a religious controversialist, and a bibliophile who bequeathed his library to the Venetian Senate.
Hans (Johann/John) Müller (1436-76), who would later become known by the Latinization of the name of his natal town Königsberg as Regiomontanus studied in Leipzig and Vienna, being a student in the latter university of Georg Peurbach (1423-61) through whom he came into the circle of Bessarion who in May 1460 was in Vienna as papal legate. With him, Regiomontanus would depart for Rome where in 1462 he not only completed an Epitome of Ptolomey's Almagest that had been begun by the now defunct Peurbach for Bessarion, but also created the present astrolabe. It was an early work. Subsequently he would write several astronomical and mathematical texts, three of them being dedicated to Bessarion, set up a printing and instrument-making shop in Nuremberg, and write at least one short treatise on the astrolabe.
The name 'Iohannis' in the inscription, the date, and the fact that it was created in Rome all cohere to suggest that the astrolabe here presented is to be associated with Regiomontanus. What the inscription does not however make clear is what, exactly, was his role. 'Ioannis opvs' need not imply that Regiomontanus physically made the instrument himself, rather than designing it for other craftsmen to execute. Nor does the inscription state that the astrolabe was actually made for Bessarion, only that it was made under his patronage. That Regiomontanus made, or had it made, as an offering to his protector is probable since he is known as a producer of astrolabes, but it cannot yet be affirmed.

Authenticity
An isolated instrument when first...