Complex sentence: Thomas Gwyn Empy Elger FRAS (1836--1897) was a British selenographer and one of the preeminent lunar observers of the Victorian age, best known for his lunar map, which was regarded as one of the best available until the 1960s.
Split into simpler sentences: Thomas Gwyn Empy Elger FRAS (1836--1897) was a British selenographer and one of the preeminent lunar observers of the Victorian age. He is best known for his lunar map, which was regarded as one of the best available until the 1960s.