Henry B. Austin was educated at Grey College, Bloemfontein, to the age of 15, after which he worked as a clerk for seven years. In October 1889 he was appointed as a clerk in the office of the surveyor-general of the Orange Free State (now the Free State), and in December 1897 rose to chief clerk and examiner of deeds in the Deeds Office. In the year the Anglo-Boer War (1899-1902) broke out he published a poem entitled Boers, British and Colonials (brotherlyness becomes comrades) (Bloemfontein, 1899). Following the British occupation of the Orange Free State he was appointed by the British administration in March 1901 as assistant registrar of deeds for the Orange River Colony and promoted to registrar of deeds in July 1905 - a post he filled until the formation of the Union of South Africa in 1910. During the resulting amalgamation of the various colonial administrations in 1911 he retired on pension. He was married to Grace Susanna Stone.
Austin's hobbies were astronomy, photography, gardening, and science in general. He was elected a Fellow of the Royal Astronomical Society in January 1908), and was a Fellow of the Royal Colonial Institute, a member of the Society of Arts of London, and a freemason. In 1903 he joined the recently established South African Association for the Advancement of Science and during its meeting in Bloemfontein in 1909 read a paper on "The tercentenary of the telescope". The paper was not published in the Report of the meeting. Also in 1903 he joined the Philosophical Society of the Orange River Colony, which was founded that year, and read two papers on astronomy of which summaries were published in its Transactions. One was titled "The glory of the heavens" (Vol. 1, 1903-7, p. 46), while the other dealt with "Comet Daniel" (Vol. 1, 1903-7, p. 70).