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The Rotunda Museum at night

The Rotunda Museum at Lowell Observatory. Mike Thompson.

The Rotunda Museum

Housing some of the most precious artifacts of Lowell Observatory's history, the Rotunda Museum was completed in 1916 and served as the institution's library until the mid-1970s.

The Rotunda features several important displays concerning:

- the discovery of Pluto in 1930 by Clyde Tombaugh, including the blink comparator he used to examine the images he was taking with the 13-inch Pluto Discovery Telescope;

- V.M. Slipher's discovery of large recessional velocities of galaxies starting in 1912 (that led ultimately to the realization our universe is expanding); this display includes the spectrograph he attached to the 24-inch Clark Telescope to conduct his research;

- Lowell Observatory's role in NASA's moon-mapping efforts for the Apollo Program, which were partly conducted with the Clark Telescope. Maps were created on campus, and many noted astronauts visited Lowell during a training session in 1963;

- Percival Lowell's research of Mars – including notes, drawings, and globes – and the influence his work continues to have, both on scientific research and popular culture;

- and the Lowell family and its rich history.

The Rotunda is also home to various measurement and calculating devices, including the Millionaire, a precursor to the modern computer, and a Thacher's Calculating Instrument, a huge slide rule (the precursor to calculators) with a folded scale 60 feet in length. You'll also find Percival's first telescope, given to him at age 15, which he took with him while traveling around the world.

Lastly, suspended from the ceiling of the dome is the Saturn Lamp, a stained-glass marvel constructed in 1918 by the Los Angeles Light Company.

 Visitor Info


Covers day and evening programs; reservations not needed.

Adults: $12

Seniors, AAA, college students: $11

Ages 5–17: $6

Under 5: Free

Members: Free

For general questions about our day and evening programs, call the Visitor Center at (928) 233-3212 during open hours (listed below).

Groups of 15 or more are eligible for a group discount; to qualify, you must make reservations at least 3 weeks in advance. Contact Samantha Flagg by email or phone at 928-856-9484.

2015 Hours

Monday through Saturday
10 a.m. - 10 p.m.

10 a.m. - 5 p.m.

Arizona observes Mountain Standard Time year round.
Click here
for the current time in Flagstaff, AZ.

Extended Hours in 2015

Feb 15, 2015 - Open until 10 p.m.

Special Closures in 2015

Jan 1, 2015 - Closed all day

Nov 26, 2015- Closed all day

Dec 25, 2015 - Closed all day