Chappe d’Auteroche was assistant astronomer at the Royal Observatory in Paris when he was asked to form part of the bevy of astronomers being dispatched to various parts of the globe to observe the transit of Venus in 1761. Recording and measuring the transit accurately was considered a crucial part of the ultimate goal to measure the solar system, and the previous transit had been in 1639. Chappe reached Siberia on 18 May, in time to observe a lunar eclipse, and the transit on 6 June. The weather was fine, so that he was able to observe the entire cycle. He and his party had to be protected by Cossacks while they worked, since the indigenous population blamed them for the unseasonally high floods, claiming that they were disturbing the sun.