William Henry Smyth started a career at the Royal Navy and served in the Mediterranean during the Napoleonic wars. In 1815, he married Annarella, the only daughter of T. Warington, Esq., of Naples; she was his companion and assistant in all his scientific works. In 1817, during a hydrographic survey, he stayed at Palermo, Sicily, where he met the Italian astronomer Piazzi, who was already famous because of his 1801 discovery of the first asteroid, Ceres. His interest in astronomy was enhanced by a visit in Piazzi's observatory.
In 1825, Smyth retired from the Royal Navy and settled in Bedford, England, where he established a fine private observatory, equipped with a 6-inch refractor. During the 1830s, he used this instrument vor observing a variety of deepsky objects, including double stars, clusters and nebulae, and kept careful records of his observations. He published his observations in 1844 in his still famous Cycle of Celestial Objects. This work was awarded with the gold medal of the Royal Astronomical Society and a presidency of this society for one two-years term. The first volume of this work was on general astronomy, but the second volume became known as the Bedford Catalogue and contains Smyth's observations of 850 deepsky objects (as well as comments of some more), a source of exhaustive informations on deepsky objects as it was available at its time. This book was published several times, the last edition by George F. Chambers in 1881. The astronomical value of this work results from the high acuracy of the positions which Smyth had obtained by his micrometer measurements.
Having completed his observations in 1839, Smyth removed to Stone, Aylesbury, and his observatory was dismantled, the telescope sold to Dr. Lee and re-erected at the Hartwell House in a new observatory designed by Admiral Smyth. Smyth still had occasion to use this instrument as his residence at St. John's Lodge was not far from its location, and again did a large number of astronomical observations in the time from 1839 to 1859.
After suffering an attack in early September, 1865, Smyth seemed to recover and on September 8, showed and explained planet Jupiter to his young grandson, Arthur Smyth Flower. A few hours later, Admiral Smyth died in the early morning of September 9, 1865 at age 78, in his home in St. John's Lodge, Cardiff. He was buried in the little churchyard at Stone near Aylesbury.
The astronomical community has honored William Henry Smyth not only by naming a Lunar crater, but a whole Mare after him, in 1935: Mare Smythii, situated 1.1N, 87.5E, and measuring 373 km across.