The H.S. Mendenhall Observatory

Aerial Photo of Mendenhall Observatory

Aerial Photo of Mendenhall Observatory


Oklahoma State University's observatory is situated under dark skies southwest of Stillwater, Oklahoma. Pictured above and at right are its site, dome, control building, and telescope, which is the largest and most advanced telescope within 300 miles.


The telescope was designed and instrumented for astrometry, photometry, and multicolor imaging of objects such as near-Earth asteroids, transiting exoplanets, and quasars. Visit the 24-inch Telescope Gallery to view the first test images made with it.


Additionally, the observatory's portable, 8- and 14-inch telescopes are perfect for visual observing, especially by OSU's introductory astronomy students. Work done by physics and engineering majors with the 14-inch telescope while it was mounted in the dome helped secure Air Force funding for the 24-inch telescope. The 14-inch Telescope Gallery shows those students and their work.


The observatory's layout is derived from a conceptual design by Stanly E Black, AIA, Architect, Boston, Massachusetts. It provides ample space for outdoor viewing and future structures.


Observatory Construction News and Future Plans

Updated April 3, 2019


The rectangular control building completes the observatory as planned. It contains a restroom, kitchenette, telescope control room, and equipment storeroom, all heated and cooled. The observatory is thus well-suited for research and instruction.


Thanks to generous private support, the control building was built in phases between 2016 and the end of 2018. Construction included the sidewalk between it and the central observing pad, the semicircular screening fence for blocking wind and stray light, and the septic system. Receipt of pending certifications will signal official completion. The finished observatory will enable OSU to introduce an astronomy minor, unique in Oklahoma, that incorporates modern observatory experience. Students who minor in astronomy and major in physics, engineering, or related fields will be ready for exciting, well-paying employment after graduation in industry, science, and defense.

It is presently necessary to upgrade the telescope's complex control system, which has been experiencing normal physical and technological aging over the years. External grant funding proposals for this are pending and also in preparation. If you would like to assist, please click here to make an instant donation to OSU Foundation account 22-40400, or contact Dr. Peter Shull and the OSU Foundation.


The Observatory on YouTube and TV

Click here to see the observatory on YouTube. This 6-minute video includes action shots of the telescope and dome, and interviews featuring OSU's president and two undergraduates.


The observatory also appears in the five-part series titled "Wonders of the Solar System" produced by the British Broadcasting Corporation (BBC). The observatory appears in the second episode, "Order out of Chaos". The series premiered in the UK and USA, and is available on DVD. To see photos of the BBC's visit to Stillwater, click here.



Stillwater Clear Sky Chart

Use the Stillwater Clear Sky Chart below to view a map of expected weather conditions for the Mendenhall Observatory. First click on the chart below. In the window that then opens, clicking one of the little squares in the top row will display a map of predicted cloud cover for the corresponding date and local time.


The Stillwater Clear Dark Sky Calendar



Dr. H.S. Mendenhall

Dr. H.S. MendenhallThe observatory is named for Harrison Shepler Mendenhall, Oklahoma State University's first astronomer.


Dr. Mendenhall earned his Ph.D. in astrophysics at the University of California at Berkeley, and served on OSU's faculty as a professor of mathematics and astronomy from 1937 until his retirement in 1968. During World War II, he taught navigation to countless air cadets as a lieutenant and captain in the U.S. Army Air Corps. Dr. Mendenhall died on March 20, 2000, at the age of 97.



Dr. Mendenhall's Personal TelescopeThis photograph shows Dr. Mendenhall's personal telescope, a 4-inch refractor built in the early 1890's, set up on the central observing pad.