This article is an attempt to elucidate this rather unknown facet of his legacy by referring to the instruments, methods and techniques he used to collect his data and the high premium he put on the accuracy of his observations. Attention is also given to his lifelong friendship with HM Astronomer at the Cape, Sir Thomas Maclear to whom he regularly sent his observations to be checked and his occasionally tempestuous relationship with the official cartographer of the Royal Geographical Society, John Arrowsmith.