Theodor Jacobsen Observatory, Astronomical observatory at University of Washington, Seattle, United States.

The Theodor Jacobsen Observatory is an astronomical observatory located on the University of Washington campus in Seattle. It houses a six-inch Brashear lens telescope mounted on a Warner and Swasey equatorial frame, all contained within a rotating metal dome.

The observatory was built in 1895 using leftover Tenino sandstone blocks from Denny Hall, making it the second-oldest building on the University of Washington campus. In 1891 the state of Washington provided $3,000 for the first observatory, and astronomy professor Joseph Taylor visited the Lick Observatory to confer with Professor Schaeberle about the instruments to be purchased. The lenses were made by John Brashear and the mechanical parts by Warner & Swasey; Taylor designed the wooden structure, which two local carpenters assembled.

The observatory welcomes visitors for regular viewing sessions where people can look through the telescope and learn about the night sky. These events bring academic science and the community together, making astronomy accessible to anyone who wants to watch the stars.

Public access follows a fixed pattern: the observatory opens every first and third Tuesday from April through September. The transit room sits on the west side of the building, and the 45-seat classroom added in 1912 is on the south side. The dome and telescope are reached on foot within the campus, so allow time to walk there.

The observatory's telescope is a six-inch Brashear refractor on a Warner & Swasey equatorial mount. The building was constructed in 1895 from leftover Tenino sandstone blocks from Denny Hall, making it the second-oldest structure on the University of Washington campus.