Astrolabe Catalogue

 

Small image of astrolabe back with rules or alidades removed. Click to enlarge.
Date 14th century
Place Sicily (?)
Material Brass
Inventory no. 50769
Acquisition Presented by J. A. Billmeir in 1957

Back


The back contains a common set of scales. The names of the months are, however, noteworthy. In particular, note the spelling of May and the use of 'n' in September, November and December. A number of the North African astrolabes in the collection transliterate the month names into Arabic substituting an 'n' for the 'm' in these months.

The back contains 5 scales of the following types:
Type
(click to view scale details)		 Range & Units Numbered Geometry Location
Degree 0 - 90, Degrees Every 5 degrees Circular, concentric The entire outer circle on the back of an astrolabe.
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 First day of month - Last day of month, Days of year Every 5 days Circular, eccentric Circular scale second in from the outer scale - refers to the full circle.
Unequal hours 1 - 6, 1/12 of daylight Every 1 hours Arc The upper two quadrants of the back of the instrument
Shadow square 1 - 12, Fingers Every 2 fingers Box The lower two quadrants of the back of the instrument
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