Government observatories of the nineteenth century were not generally important sites of experimentation and research. Experimentation was something more likely to be found – in Britain at least – in a private observatory or laboratory. But the case of the transit of Venus would be different. Although the general plan to be followed was 200 years old, and although the basic set-up would be the same as it had for the transit of 1769 a century earlier, the astronomers preparing for 1874 faced major unknowns. During the four years between the establishment of the programme and the day of the transit of Venus, preparations would consist largely of time-pressured research and experimentation into these unknowns. The highly-refined surveillance of celestial motions that defined Greenwich astronomy would be supplemented with speculative experimental investigations into subjects ranging from conductivity in telegraphic wires to the shape of the sun to the properties of photographic emulsions. Greenwich would come to look more like the private astrophysical observatories of men such as Norman Lockyer, and in the process Airy would enlist the help of some of the most prominent amateur astronomers.

The direction and scope of research was shaped by a number of issues, with the dominant concerns circling around the black drop phenomenon. In the early 1870s there also emerged new theories about the physical nature of the sun that bore directly on the black drop and other key issues, especially those relating to photography. Photography was just one of a whole new range of technologies available for making different sorts of approaches to the transit of Venus measurements, and by and large these technologies would have to be applied in new and untested ways. At almost every stage in the development of the programme there was virtually no clear agreement among the experts from different nations about the best way of proceeding.

While the programmes in France, Germany and the United States were organized around commissions, in Britain Airy was the sole manager. He described his management philosophy to Arthur Auwers at the Berlin observatory in 1873: The British arrangements for the transit of Venus do, in fact, rest with me.