(music-news.com ) - Robbie Williams is planning to splash out ?2.5 million on an alien observatory. The 34-year-old pop singer has been spending all his free time visiting Arizona's National Optical Astronomy Observatory, in Tucson, and he now plans to build his own viewing station so he can monitor the skies for UFOs whenever he wants. A source said: "He is leading a bizarre existence at the moment, vanishing into the desert to look at stars in far-flung galaxies. He is dead set on buying himself an observatory in the desert, which can cost up to ?2.5 million. He is hooked on all things from outer space." Robbie - whose 2006 'Close Encounters World Tour' was alien-themed - recently revealed he was planning to make his obsession a full-time profession. He said: "Seriously, I want to go out and investigate these things. I'm stopping being a pop star and becoming a full-time ufologist." The 'Angels' star claims he has been visited by spaceships on three occasions. Describing one encounter of the third kind, he said: "I was lying on my sun lounger outside at night. Above me was a square thing that passed over my head slightly and shot off."