The introduction into the laboratory of the magic lantern and the arts of projection marked a change from putatively individual and mechanical to obviously collective and skillful perception in nineteenth-century German sciences. In 1860 Karl Friedrich Zöllner introduced an astro-photometer to astronomers who, by practising with it, became aware of their own tacit and ubiquitous skills. Zöllner was a showman who was aware of the personal skills involved in magic-lantern projection. Like showmen, nineteenth-century astronomers could also control and calibrate their vision with this instrument. Photometrists such as Zöllner were not only aware of subjectivity, but developed techniques to manipulate, control and to employ it in scientific judgements. This view stands in contrast to that of the scientists described by Lorraine Daston and Peter Galison, for whom ‘machines offered freedom from will – from the willful interventions that had come to be seen as the most dangerous aspects of subjectivity’. But with Zöllner's successful programme of instrumental subjectivity, acts of willful intervention were at the very centre of astronomical judgement.