An observatory was a structure used for the study of astronomical phenomena.
Jodrell Bank Observatory detected the return of the planet Mondas to the solar system in 1986. Mount Palomar Observatory offered the first pictures of Mondas to the International Television news. (TV: The Tenth Planet)
In 2014, an observatory at Mount McKerry on the island of St Albans detected the approach of the Stormcrow and dealt with the No Things with the aid of the Fourth Doctor and Leela. (AUDIO: Night of the Stormcrow)
An observatory was one of the few surviving remnants of the Heavenite civilisation by the time of Bernice Summerfield's archaeology expedition on Heaven in the 26th century. (PROSE: Love and War)