William Ronald, a captain in the British Army, applied for the position of assistant at the Royal Greenwich Observatory, London, in 1824. At that time an assistant was also required by Reverend Fearon Fallows* at the Royal Observatory, Cape of Good Hope, to succeed Patrick H. Scully*, and Ronald offered himself for that post also. The Astronomer Royal, John Pond, interviewed Ronald and found him "perfectly competent to undertake either of the situations for which he applied" (Warner, 1995, p. 145). On Pond's recommendation the British Admiralty (which funded the Cape Observatory) approved his appointment as first assistant at the Cape on 1 December 1824. Before leaving he was required to inspect the transit instrument and mural circle that were being constructed for the observatory in London, and was employed for some time at Greenwich to become familiar with such instruments. His departure was further delayed so that he could accompany the new instruments to the Cape. During this time, in August 1825, he determined the oscillation period of a compound pendulum at Greenwich and brought the pendulum to the Cape with the other instruments. It was used by Fallows to determine the acceleration due to the earth's gravity at the Cape Observatory, relative to that at Greenwich.
Ronald eventually arrived in Cape Town in November 1826, but does not appear to have been of much assistance to Fallows. By 1827 he was a member of the Cape of Good Hope Horticultural Society (founded in 1826). During 1830 the staff of the observatory suffered from scarlet fever and Ronald also became ill. He left the observatory on sick leave in August 1830 and returned to England in October that year to recuperate. However, he resigned his position in March 1831. The post was subsequently filled by Lieutenant William Meadows*. Ronald and his wife Elizabeth had at least one daughter, born at the Cape in 1828.