Ray system of Tycho lunar crater, 1900. The Tycho crater (upper right) is 86 kilometres across, with the rays formed by ejecta from this major impact event that took place 108 million years ago. The rays can be up to 1500 kilometres long. This image is from an edition of the atlas of lunar photographs produced by French astronomers Maurice Loewy (1833-1907) and Pierre Puiseux (1855-1928). The observations were made from the Paris Observatory in Paris, France. This observation was made on 10 September 1900.