Tour Groups and Bus Tours

Built in 1928-1929 expressly for the purpose of completing the search for “Planet X” – the name for the hypothetical ninth planet in the solar system that Percival Lowell thought must exist – this telescope, like the Clark, is one of the most famous telescopes in the history of American astronomical research.

Learn more about the Pluto Discovery Telescope.

Perhaps the most critical instrument Lowell acquired during these early searches was a blink comparator machine. This specialized stereo microscope held the photographic plates side-by-side. A mechanical shutter allowed the observer to alternately see first one image and then the other while looking through a microscope eyepiece. The instrument was originally designed to hold 6” x 7” plates, but Lowell staff found they could more proficiently examine the sky using 14” x 17” plates. Lampland modified the apparatus accordingly by designing slip frames allowing for a quarter of the large plates to be examined at a time.

Nineteen years after the purchase of the blink comparator, Clyde Tombaugh used it to discover Pluto.

The Clark Refractor is one of the most storied telescopes in the world, an important piece of scientific, cultural, and American history.   Percival Lowell famously used it in his controversial studies of Mars, research that Lowell openly shared with the general public as well as the scientific community.

Progressive research with the Clark continued into the 1960s, when scientists and artists combined their talents to create detailed maps of the Moon. These were critical to understanding the physical characteristics of the lunar surface and were used in support of the Apollo astronauts’ journeys to the Moon. Not only that, but as part of their training, several of the moonwalkers peered through the Clark to familiarize themselves with craters and other lunar features.

The exploration of Mars, the Moon, and the expanding universe is just part of the Clark’s story. It also played an important role in building public awareness and excitement about space, from the casual, walk-in visitor to educational programming by the likes of Walt Disney, Carl Sagan, and Bill Nye the Science Guy.

The Giovale Open Deck Observatory at Lowell Observatory features one of the finest collections of telescopes available for public observing. This public observing plaza features six advanced telescopes that collectively give you a viewing experience that goes far beyond seeing faint smudges of light. From rich star fields and planets full of color, to nebulae and galaxies that reveal obvious structure, the famously dark skies of Flagstaff are abundant in celestial treasures for you to discover.

The Giovale Open Deck Observatory also features daytime exhibits that highlight the science of spectroscopy, the types of telescopes astronomers use and how to preserve dark skies in Arizona and beyond. A set of six plinths along the perimeter of the observing plaza align to the locations of the Sun during sunrise and sunset on the equinoxes and solstices.

Named for longtime Lowell Observatory philanthropists John and Ginger Giovale, the Giovale Open Deck Observatory will leave you feeling more connected to the night sky and all the wonders that it holds.

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.

Click here to see which exhibits are currently on display in the Rotunda Museum.