The Theodor Jacobsen Observatory is the on-campus observatory of the University of Washington. Built in 1895, it is the second oldest building on campus and was constructed using the remaining Tenino sandstone blocks from Denny Hall, the oldest and first building on campus. The refracting telescope, enclosed within the dome, has a 6-inch Brashear objective lens on a Warner & Swasey equatorial mount. The observatory also includes a transit room on the west side and a 45-seat classroom, which was built later, on the south side. Today, the observatory is primarily used for public outreach and is run jointly by the UW Department of Astronomy and the Seattle Astronomical Society. Every first and third Wednesday between April and September the observatory is open to the public. The observatory is listed on the State Register of Historical Buildings. Information on the original design and building of the observatory by Prof. Joseph Marion Taylor may be found on the University of Washington Astronomy Department website and other sources. See also List of observatories References External links Official Website (updated 2019-Apr-25) Seattle Astronomical Society Website Astronomical observatories in Washington (state) Public observatories University of Washington campus 1895 establishments in Washington (state) Buildings and structures completed in 1895