Astrolabe

Georg Hartmann (1489-1564) moved to Nuremberg, an important centre for the production of scientific instruments, in 1518 and was probably the most prolific instrument maker during the first quarter of the 16th century. It is not surprising, therefore, that some characteristics of his astrolabes appear to betray an emphasis on quantity rather than quality. He never engraved letters or numbers, but used punches instead.

The triangular throne is cast as one piece and is composed of three sculpted circles, or roundrels, which give the appearance of flower petals. The upper roundrel is pierced, so that it can hold the shackle with the swivel, pin and ring. The throne is soldered to the rim, which in turn is riveted to the mater. The rete, which follows a design characteristic of Hartman, has 27 needle-shaped star pointers. There are three plates with stereographic projections for the following latitudes: 39/42º, 45/48º and 51/54º. On the back of the instrument is a combined scale for degrees and the zodiac and a calendar scale. Within these scales, the back is divided into two halves: the upper half features a diagram for the unequal hours and the double-headed eagle of Austria. The coat of arms of Nuremberg is positioned at the centre and the lower half displays a double shadow square. Underneath this is the signature: 'GEORGIVS HARTMAN NORENBERGAE FACIEBAT ANNO MDXLVIII'.

Credit: National Maritime Museum, Greenwich, London, Caird Collection