In 1887 observatories worldwide embarked on an ambitious project to photograph the entire sky, cataloguing the positions of millions of stars to produce a document known as the Astrographic Catalogue. The project was raised at the 1887 Astrographic Congress in Paris with more than 50 observatories committing to the project. Each observatory was allocated a unique part of the sky to map. Sydney Observatory was assigned a section of the sky that included the Southern Cross and a large part of the Milky Way.
The tools and methods of mapping were standardised across the participating observatories and represented the most cutting-edge science. Photography revolutionised the study of astronomy and made possible the ability to detect faint stars and document up to thousands of stars at a time. Using a special kind of telescope known as an astrograph, photographic plates were exposed to starlight to produce images of the sky. The positions of the stars were measured over decades by groups of women known as ‘computers’.
The final volume of the Sydney Section of the Astrographic Catalogue was published in 1964. Throughout the 70 years it took to complete, Sydney Observatory measured more than 430,000 stars. Australia’s participation in this grand astronomical project placed the colony on the international stage, representing a major contribution made by Sydney Observatory during its research years.