8 July 1999
A UNIQUE EARLY 17TH-CENTURY GERMAN BRASS ASTROLABE
Signed and dated 'Thomas Pregel von Nor: Fecit in Zwickau Ao 1629' International Checklist No. 560
The limb is attached by rivets to the back with which the throne, with shackle and ring, is integral. The mater is engraved with a stereographic projection for the latitude of 52. A separate plate is engraved for the latitudes of 48 and 50. The reverse of the astrolabe is completely blank. All the numbers on the instrument are punched.
The limb is divided with the following scales. Hours to one minute of time numbered in quarter hours, the whole circle labelled in 24 hours in roman numerals, with XXIIII at the top. Labelled, secondly, in arabic numerals in twice 12 hours, with 12 at the top. Next is the scale of degrees, divided into 20 minutes of arc, labelled in two sequences 0-90 in quarters, and 360 beginning at the left side. Additionally there are the arcs for the Houses of Heaven. The fineness and accuracy of the divisions is remarkable.
The mater and the separate plate have almucantars at 2 intervals, and azimuths at 5. For each is a thick line with subdivisions to 1, alternatively shaded. Two sets of hour lines are engraved for planetary hours, marked 'Horae ab Ort Solis' and 'Horae ab Occasu Solis'. Curves showing the tropics and twilight are present.
The rete is unusual in the fineness of the filigree connecting the ribbons for the star names. Two cross bars run North-South and East-West (on one of which is the signature). There are two circles of which one is the ecliptic, divided in single degrees and into the Zodiac, the other circle represents the equator, which is divided in single degrees numbered in tens to 360. A screw and wing nut hold the rete in place; no alidade is present.
11 in. (28.8 cm.) diam.; in. (0.5 cm.) thick
Rothschild inv. no. AR2637.
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1903 Theresianumgasse Inventory, p. 92, no. 218.
1905 Theresianumgasse Inventory, p. 38, no. 159.
Zinner, Deutsche und niederlndische astronomische Instrumente des 11.-18. Jahrhunderts, Munich, 1956, pp. 472-3.
Thomas Pregel is not known apart from this astrolabe and an astronomical compendium also dated 1629 (see Zinner, loc. cit.).
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