Perkins Observatory, in Delaware, Ohio, USA. Is an Observatory used to study astonomy and space. It was built in 1923, using money left by mathmatician, Hiram Perkins. Aftwerwards, the Observatory became managed by the Ohio State University. The Observatory became famous among astronomer's who travelled around the world to use the telescope. Philip Keenan worked at the Observatory, during his time there, Keenan developed the MK System of Stellar Classification (The classification used to classify stars). The MK System is the most common form of Stellar Classification used today.