the crater rays spread as far as 800 kilometers across the surrounding mare, overlying rays from the craters aristarchus and kepler. the rays are less distinct than the long, linear rays extending from tycho, instead forming a nebulous pattern with plumy markings. in multiple locations the rays lie at glancing angles, instead of forming a true radial dispersal. an extensive pattern of smaller secondary craters can also be observed surrounding copernicus, a detail that was depicted in a map by giovanni cassini in 1680. some of these secondary craters form sinuous chains in the ejecta.