Accession No
0999
Brief Description
astrolabe, with mater, rete, rule, single latitude plate, and pin, French [attributed], 15th Century (with modern repairs)
Origin
France [attributed]
Maker
Class
astronomy
Earliest Date
1400
Latest Date
1500
Inscription Date
Material
metal (brass)
Dimensions
Mater diameter 102 mm; thickness 8 mm
Special Collection
Robert Whipple collection
Provenance
Inscription
Description Notes
Brass astrolabe, with mater, rete, rule, single latitude plate, and pin, [French], 15th century (pin is modern replacement - see XRF results).
Mater is divided on rim to single degrees, but unlabelled. 24 hours labelled numerically on edge of mater and on front of throne. Suspension ring attached. Dent 90 degrees along rim. On reverse are zodiacal and calendar scales, divided to single degrees. Outer zodiacal scale is aligned with division on front of mater. Months and signs are distinguished only by initial letters, engraved in round Gothic style. 1st point of Aries is 11th March. Shadow square of twice 0 to 12 to 0, labelled in fours [numbers appear to be in a different, later hand to rest of instrument.] Pair of unequal hour quadrants, uncalibrated.
Rete with 19 star pointers, 17 labelled in angular Gothic: vega, altair, humer9, algeuse [=betelgeuse], ecus, alteva [?], alcavier [?] (within ecliptic); spica, buca [?], cor leo, albalbor [?], rigil, ?euler ceti [?], memar [=menkar?], abebarau [=aldebaran?], albeure [=abireo?], algomesa [?] (outside ecliptic). Ecliptic divided to 2 degree units, with zodiac signs marked by initial letters in round Gothic. Construction lines visible on reverse.
Plate engraved for 35 and 42 degrees latitude.
Counter-changed rule with no divisions.
Replacement (?) pin sheared off at end.
[NOTE: On 06/12/2013 XRF analysis was conducted on this instrument. Results and analysis are given in the ‘Notes’ field and in the OHF.]
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 (see diagram above). 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.
FM:39696
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