Georg Hartmann

Georg Hartmann studied in Cologne and spent time in Italy before settling in Nuremberg, where he was vicar of St Sebald. Alongside his church duties he made astrolabes, sundials, globe gores and other instruments. Surviving astrolabes by him share near-identical plates and retes, which shows that he produced them in series using standardised, often cast or printed components — an early example of batch production of scientific instruments. He also described the inclination of the magnetic needle in a letter of 1544.

How to recognise the work: his instruments are usually signed, often in the Latin form Georgius Hartmann, and dated to the year, which makes them unusually easy to place. The workshop made brass astrolabes, diptych and other portable sundials, globes and quadrants, and printed instruments on paper to be cut out and assembled; the catalogue includes astrolabes of 1527 and 1548, diptych sundials of 1537 and a paper astrolabe of 1542.

Hartmann's own manual, the Collectanea, records how he made his dials and astrolabes; it was published in English as Hartmann's Practika in 2002. Its range is wide — block, declining, shepherd's, moon, chalice and cylinder dials, as well as gunners' levels and sights — and Levinus Hulsius credited him with inventing the gunner's gauge. All four astrolabes of one 1537 run share the same error in the altitude circles of their plate for latitude 39°, a telltale of batch production from a single pattern.

Before settling in Nuremberg in 1518 he studied theology and mathematics at Cologne and lived for some years in Rome, where he knew Andreas Copernicus, brother of Nicolaus. He noticed there that the compass needle did not point to true north, and in a letter of 1544 to Duke Albrecht of Prussia he described the dip of the needle; the letter was not published until 1831.