In 1845 he completed a 24-inch (0.6-m) telescope, the first sizeable reflector to be mounted equatorially, with which he discovered several planetary satellites. He found Neptune’s largest, Triton, in 1846, just 17 days after the planet’s discovery. In 1848 he discovered the Saturnian satellite Hyperion independently of (but two days after) W. C. Bond and G. P. Bond, and in 1851 he discovered Ariel and Umbriel orbiting Uranus. From 1862 to 1864, observing from Malta with his 48-inch (1.2-m) reflector, he and the German-born astronomer Albert Marth (1828–97) found 600 new nebulae.