Accession No
0305
Brief Description
astrolabe, in gilt copper, with case, purportedly by Johannes Bos, 1597, but actually a c. 1920 fake
Origin
Netherlands; Amsterdam [possible, see Price 1956]
Maker
fake, unknown maker Johannes Bos [purported]
Class
astronomy
Earliest Date
1920
Latest Date
1920
Inscription Date
1597
Material
metal (brass, copper); wood; hide (leather)
Dimensions
case diameter 120 mm, thickness 20 mm; astrolabe diameter 100 mm
Special Collection
Robert Whipple collection
Provenance
Bought by Robert Stewart Whipple from Gertrude Hamilton (trading as “Mercator”), Paris, on 20/04/1928. Copy after the original in the Mensing Collection.
Inscription
IOHANNES BOS DIE 24 MARTII 1597 (Rete)
Description Notes
Gilt copper astrolabe with rete, rule, alidade, screw-pin and nut, single latitude plate, case.
Mater is formed from two parts, disc and ring. Simple throne riveted to mater holds suspension ring with hook. Rim is marked with degree scale (90-0-90-0-90) marked in tens,and hour scale of twice twelve. Very poor subdivision with scratch marks to single degrees. On reverse are degree & zodiac and calendar scales, and shadow square. Degree & zodiac scale is labelled with astrological signs, poorly divided to single degrees, and marked in tens; degree scale 90-0-90-0-90. Calendar scale has months marked by single letters: G, F, M, A, M, G, I, A, S, O, N, D. It is poorly divided to single degrees, and labelled in tens. First point of Aries is near 21st of March. Shadow square twice12-0-12-0 is divided to units and labelled in threes. Its three sides are decorated with wind faces, and there is a sun-face on the fourth side.
Rete has ecliptic marked with astrological house signs, and poorly divided into two degree (?) units, but with no house boundaries marked. 33 star pointers, labelled: ART, P. C. 0 M. 2, EL.C.V.M.2, IL. VR. M. 2, HIRCUS, CA AL2, P.CA S.S.5, C.DR.3, C.CIG 2, AQUILA.V, SELIRAE.I, FIDICULAI, C.HER.3, L.CO.2 (WITHIN ECLIPTIC); C. CAPR.3, AUST, 3, VENTER CETIS, ALDEB, OC.TAURI, RIGEL.I, SIN.PES.ORIONIS, D.HUMOR.I, MED.COR.2, CANIS MINOR, PROCI OHI, LUCIDA IDRAE 2, COR.L.EONIS, SPICA.VIRGI.I, R.CORVI.3, ALA.DC.3, COR 8 2 (outside ecliptic). Other astrological signs are marked on rete also.
Plate engraved for latitudes 43 and 44.
Counterchanged rule poorly divided, and marked only 10.
Case of leather-covered wood with brass hinges.
Good condition, with some wearing of the gilt. Case is cracked and damaged but integral; catch no longer works.
[NOTE: On 15/04/2015 XRF analysis was conducted on this instrument. Results and analysis are given in the ‘Notes’ field.]
References
Events
Description
An astrolabe is a model of the heavens with the earth placed at the centre. A section of the heavens is projected on to the astrolabe. The co-ordinates of stars and planets are depicted on a grid called the rete. The earth is represented by latitude plates of which there are more than one. This is because the movement of the stars depends upon the latitude of the place from where the observation is made. Cambridge has a latitude of 52°, Rome 42°, Madrid 41°, and Paris 49°. Each latitude plate has circles and lines engraved on them which include the tropic of Cancer and Capricorn, the equator and a twilight line. The rete and latitude plates are housed within the mather which has a raised edge called the limb. On European astrolabes the limb is engraved with a degree scale showing 0° to 360° and / or a scale of 24 equal hours.
On the back of the astrolabe are engraved several scales including a calendar scale and a shadow square. On Islamic astrolabes extra scales and tables are engraved for finding the direction of Mecca (for times of prayer). At the back of the astrolabe is also the alidade. The alidade has sights through which an astronomer would take simple observations of the sun or of a particular star, to find the time of day or night. The sights can also be used for finding the heights of buildings, trees or hills.
From display label:
This astrolabe purports to have been made by Johannes Bos in 1597, but is in fact a copy of an original from the notorious collection of Anton Mensing. Although most of Mensing’s instruments that have found their way into museum collections worldwide are geniune, a significant number of forgeries have been identified.
Whipple purchased three Mensing objects that are now known to be forged. Generally the best indicator of a forgery is poor execution: in this case the exceptional workmanship of Bos has not been matched; moreover the original of which this is a copy is known.
FM:42600
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