Tycho Brahe's instrument for measuring angular distances, 1569.
© Science Museum / Science & Society Picture Library
'Instrumentum pro distantus', plate taken from Danish astronomer Tycho Brahe's 'De Nova Stella Anni' (Vol 2, p 337, 1572'). Considered to be the greatest pre-telescope observer, Brahe's (1546-1601) contributions to astronomy were enormous. Not only did he revolutionise astronomical instrumentation, by emphasising the importance of accuracy for the first time, but also profoundly changed observational practice. He was the first to observe the obrits of the moon and planets, and the first to make corrections for atmospheric refraction.