Astrolabe Catalogue

 

Small image of astrolabe back with rules or alidades removed. Click to enlarge.
Date 16th century (?)
Place North Africa
Material Brass
Inventory no. 37527
Acquisition Lent by the Bodleian Library, Oxford, in 1952

Back



The back contains 7 scales of the following types:
Type
(click to view scale details)
Range & Units Numbered Geometry Location
Altitude 0 - 90, Degrees of arc Every 5 degrees Circular, concentric Upper right quadrant of outer circular on back of instrument.
Altitude 0 - 90, Degrees of arc Every 5 degrees Circular, concentric Upper left quadrant of outer circular on back of instrument.
Zodiacal signs 0 - 30, Zodiacal divisions, equal or unequal Every 5  Circular, concentric Circular scale immediately inside the outer scale - refers to the full circle
Calendar Days of year  days Circular, concentric Circular scale second in from the outer scale - refers to the full circle.
Unequal hours 1 - 12, 1/24 of daylight Every 1 hours Arc Upper left quadrant (inside circular scales)
Sine/Cosine 1/60 of quadrant radius Not numbered  Angle Upper right quadrant (inside circular scales)
Shadow square 0 - 12, Fingers Every 3 fingers Box Left hand vertical 'face' of the shadow square (in LL)
Shadow square 0 - 12, Fingers Every 3 fingers Box Right hand vertical face of the shadow square (in LR)
Shadow square 0 - 12, Fingers Every 3 fingers Box Left hand bottom face of the shadow square (in LL)
Shadow square 0 - 12, Fingers Every 3 fingers Box Right hand bottom face of the shadow square (in LR)
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