Source: Proceedings of History Week. (1981)(108-109)

[p.108] William Lassell in Malta (1861-1865)

Paul J. Micallef

During the nineteenth century, an amateur British astronomer set up in Malta the world’s largest telescope and spent many years observing and discovering celestial bodies at Tigne Barracks in Sliema.

William Lassell was born at Bolton, England, in 1799 and spent his early years constructing telescopes of moderate dimensions. In 1844, Lassell started to modify and to perfect systems of mirror polishing which was considered as a very delicate and laborious task in the astronomical field. Through hard work and self confidence, W. Lassell designed a two-foot telescope and on the 10th of October 1846 discovered Triton, a satellite of the planet Neptune. Other spectacular results were announced when Lassell discovered Hyperion of the planet Saturn and the satellites Ariel and Umbriel of the planet Uranus.

In 1852, William Lassell visited the island of Malta for the first time and brought with him a two-foot diameter telescope which measured twenty feet in length. This telescope, which was already an achievement in design and performance, was stationed on St. John Cavalier in Valletta.

In 1861, Lassell returned to Malta with a four-foot diameter telescope. The instrument was the world’s largest telescope, which had a length of thirty-seven feet and was mounted at Tigne Barracks in Sliema. The telescope was a Newtonian reflector and the tube consisted of an iron lattice with ribs fitted at equidistant spaces. The reason for this open type design was to compensate and stabilise expansions due to the difference in internal and external temperatures of the telescope.

A wooden tower with a built-in stair case was constructed adjacent to the telescope and the observer had ample space to make the necessary observations at any desired position. Two Maltese workmen helped Lassell to drive the telescope with the aid of hand operated gear wheels. The British Navy was commissioned to deliver the huge telescope to Malta after recommendations by Lassell’s friends to influential people in England. It is interesting to know that Lassell’s discoveries in Malta include six hundred nebulae and the variable star ‘S’ Pegasi. These discoveries were made with the collaboration of Albert Marth who was a professional astronomer in Ireland.

In 1870, William Lassell was elected president of the Royal Astronomical Society and the University of Cambridge awarded him with the honorary LL.D. [p.109] degree. Other institutions honoured Lassell and the astronomer continued an active life in the astronomical field till his death in 1880.

Two moon craters were named after Marth and Lassell. William Lassell crater is found adjacent to Mare Nubium and Albert Marth crater is situated near the edge of Mare Humorum.

In 1975, I recommended to the Street Names Committee of the Works Dept. that a street should be named in honour of W. Lassell. On the 12th December 1975, the Malta Govt. Gazette brought a notice that a road in Fgura was named William Lassell Street.

REFERENCES:

William Lassell:— Observations of Plantes and Nebulae at Malta — Public Lib.

William Lassell:— Lettera sulla Nebula Planetaria — Public Lib.

Despatches from Secretary of State to H.E. Sir J. Gaspard Le Merchant, Governor of Malta (1861).

Isaac Asimov:— Eyes on the Universe — Public Lib.

Monitore Geografico Scientifico di Malta (Ottobre 1887) — Public Lib.

Malta Govt. Gazette — 12/12/75.