The PAGASA Astronomical Observatory which is located inside the campus of the University of the Philippines, Diliman, Quezon City.  It is equipped with a 45-cm. computer-based telescope donated by the Japanese Government thru its cultural- grant-aid program.  It is the biggest ever acquired by the PAGASA since the establishment of the observatory in 1954 and is now the largest operational telescope in the country.  It is very powerful that astronomers and astronomy enthusiasts may now conduct effective observations of stellar bodies and other distant space objects.

The principal activities at the Observatory are observations of sunspots, lunar occultations, planets and stars. It also makes observation of the satellites of Jupiter and the transits of Mercury, comets and the other planets.  At times when there are occurrences of significant astronomical phenomena like eclipses, appearances of comets and meteor showers, the Observatory is filled with visitors. Likewise, it is a venue for the educational field trips of most schools in Metro Manila and other provinces for their requests of lectures, stargazing and telescoping sessions. Overnight stargazing and telescoping sessions are conducted at the Observatory upon request.

From 1980 to 1984, the observatory made observation of variable stars.  It observes astronomical phenomena that are seen in the country such as the three total solar eclipses in this century, which path of totality crossed the Philippines.

 The Observatory is operational 24 hours a day, manned by personnel on three (3) shifts (6AM-2PM; 2PM-10PM and 10PM-6AM)