Lowell Observatory in Flagstaff: Where Pluto Was Found and the Stars Come Out

Some day trips are about hiking or scenery. This one is about looking up. Lowell Observatory sits on Mars Hill, just a mile west of downtown Flagstaff, and it is one of the coolest places in Arizona to spend an afternoon and evening. This is where Pluto was discovered, where an astronomer found some of the first evidence that the universe is expanding, and where you can still put your eye to a telescope that is older than the state of Arizona.

I love that it works on two levels. During the day it is a fascinating history and science museum spread across a pine-covered hilltop. After sunset it becomes a stargazing party under some of the darkest skies of any city in the country. Here is what to see, how tickets work, and my tips for planning the best visit.

A Quick History of Lowell Observatory

Lowell Observatory was founded in 1894 by Percival Lowell, a wealthy Boston businessman who became obsessed with Mars. He picked Flagstaff for its high elevation, clear air and steady skies, and he built his observatory on a mesa that came to be called Mars Hill. The campus sits at about 7,250 feet, and the observatory is a private, nonprofit research institution that is still doing real science today.

Percival Lowell is best remembered for two things. The first is his belief that Mars had canals built by intelligent beings, an idea that did not hold up but sparked huge public interest in astronomy and inspired generations of science fiction. The second is his search for a mysterious ninth planet he called Planet X. He died in 1916 without finding it, but the hunt continued, and that is where the most famous chapter of the story begins.

The Discovery of Pluto

In 1929 the observatory hired a young farm kid from Kansas named Clyde Tombaugh. He had no college degree, but he had sent in careful drawings of Mars and Jupiter made with homemade telescopes, and the staff was impressed. His job was grueling: photograph the same patches of sky on different nights, then compare the glass plates to look for anything that moved.

According to the observatory, Tombaugh took the key images in January 1930 with a 13-inch telescope built specifically for the search. On February 18, 1930, while comparing the plates with a device called a blink comparator, he spotted a faint speck that jumped back and forth between the two images. That was Pluto. The observatory announced the discovery on March 13, Percival Lowell's birthday.

The name came from an 11-year-old girl in England, Venetia Burney, who suggested the Roman god of the underworld. Staff liked that the first two letters, P and L, were also Percival Lowell's initials.

Pluto was reclassified as a dwarf planet in 2006, but don't say that too loudly in Flagstaff. The town still loves its hometown world, and the observatory celebrates it every winter.

What to See on Campus

General admission gets you into the whole campus. Plan on a couple of hours during the day and longer if you are staying for stargazing.

Pluto Discovery Telescope

This is the dome where it all happened. Inside is the 13-inch astrograph Tombaugh used to take the photographic plates that revealed Pluto. The telescope and dome were restored in 2018, and you can walk through on a self-guided visit and learn how those 14 by 17 inch glass plates were used to sweep the sky. Standing next to it is a little goosebump moment for anyone who grew up memorizing nine planets.

The Historic Clark Telescope

The 24-inch Clark Refractor was built in 1896 by Alvan Clark and Sons, and it is the instrument that made Lowell famous. Percival Lowell used it to study Mars. In the early 1900s, astronomer Vesto Slipher used it to measure the motion of spiral galaxies and found that most of them were racing away from us, some of the first evidence that the universe is expanding. In the 1960s it was used to help map the Moon ahead of the Apollo missions.

Here is the best part: it is still in use, and on clear nights the Clark is dedicated to public viewing. Looking through the same lens Lowell and Slipher used, inside a wooden dome that has been turning since the 1890s, is a highlight of any visit.

Giovale Open Deck Observatory

The Giovale Open Deck Observatory, usually called the GODO, is the modern counterpart to the historic domes. It is an open-air plaza with six advanced telescopes dedicated to public viewing, including a 32-inch Dobsonian that is the largest telescope on Mars Hill, a 16-inch Schmidt-Cassegrain, an 8-inch refractor with a striking Victorian look, and several other scopes tuned for planets, star clusters, nebulae and galaxies.

On a clear night, staff spread out across the deck with different targets in each scope, so you can wander from Saturn's rings to a distant galaxy in a few minutes. During the day the plaza has exhibits on telescopes and dark skies, plus a solar alignment display that marks where the Sun rises and sets on the solstices and equinoxes.

Astronomy Discovery Center

The Astronomy Discovery Center is the newest building on campus and a great place to start. It holds the Stardust Lab Astronomy Gallery, the Orbits Curiosity Zone for little kids, the Lowell Universe Theater with a giant curved screen, and a rooftop Dark Sky Planetarium where guides use lasers to point out constellations while you sit outside under the real sky. The Planet X Cafe is here too, with sandwiches, salads, soups and drinks, which is handy if you are staying into the evening.

Rotunda Museum and Lowell's Mausoleum

The Rotunda Museum is a charming older building filled with historic instruments, photos and artifacts from the observatory's early years. Nearby you will find the mausoleum of Percival Lowell, a blue-domed tomb on the hilltop he loved. Guided tours walk you through the history and are one of the best ways to understand what you are looking at.

Flagstaff: The World's First Dark Sky City

Part of what makes stargazing here special is the town around it. In 2001, Flagstaff was named the world's first International Dark Sky City by the group now called DarkSky International. The city has long had outdoor lighting rules that cut down on light pollution, a legacy that goes back decades and was pushed along by the observatory.

You will notice it as soon as you drive around at night. Streetlights are shielded and glow a warm amber, signs are not blazing, and the Milky Way is visible from places that would be washed out in most cities. It is a great reminder that dark skies are something a community can choose to protect.

Hours and Tickets

Always check the official site before you go, because hours, programs and prices change by season. Here is what the observatory listed when I checked:

• Hours: Lowell typically opens at noon and stays open into the evening, until about 10 pm on many nights and sometimes later on weekends. It is closed Tuesdays, plus Thanksgiving, Christmas Eve, Christmas Day and New Year's Day. Current hours are on the Plan Your Visit page: https://lowell.edu/visit/

• General admission: $35 for adults 18 and up, $30 for seniors 55 and up, $20 for kids 6 to 17, and free for kids 5 and under. It covers guided tours, exhibits, historic buildings, Lowell Universe Theater shows and stargazing for the whole day.

• Add-ons: A Dark Sky Planetarium show or a theater film is an $8 add-on, or you can buy general admission plus the planetarium for $43 for adults.

• Discounts: In-person discounts are listed for military families and Museums for All, and locals, students and members of Arizona Native Nations get reduced rates on Mondays, Wednesdays and Thursdays.

• Re-entry: Your ticket is good all day, so you can leave for dinner and come back for stargazing. Hang on to your sticker or receipt.

• Reservations: General admission does not require a reservation, but premium experiences, classes and excursions do.

Tickets and pricing are here: https://lowell.edu/visit/buy-tickets/

On-site ticket sales end at 9 pm, so do not cut it too close if you plan to arrive late.

When the Telescopes Open

Telescope viewing usually starts around sunset, which the observatory says can be as early as about 4:30 pm in winter and as late as 8 pm in summer. That makes fall and winter fantastic for families, since you can see real stars and planets before bedtime.

Viewing depends completely on the weather. Clouds, rain or snow close the telescopes, though indoor exhibits, theater shows and talks keep going. If you are driving up just for the telescopes, check the Flagstaff forecast first and have a backup plan.

Tips for the Best Visit

• Arrive in the afternoon. Come a few hours before sunset, do the daytime tours and exhibits, grab dinner, and then stay for the telescopes.

• Dress warmer than you think. At 7,250 feet, Flagstaff nights get cold fast, even in summer. In fall and winter, bring a heavy coat, hat and gloves. You will be standing outside in line for the telescopes.

• Wear comfortable shoes. The campus is spread out, with some uphill walking between the domes.

• Leave the dog at home. Pets are not allowed on campus. Service animals are welcome.

• Go easy on lights. At night, keep phone screens dim and skip flashlights unless they are red. Your eyes need time to adjust to the dark, and so does everyone else's.

• Pick a moonless night for galaxies. A bright Moon is gorgeous through a telescope but washes out faint objects. Around new Moon, the deep sky views are best.

• Weekends get busy. Saturday evenings tend to be the most crowded. A weekday visit (not Tuesday) means shorter lines at the telescopes.

• Ask questions. The educators at each telescope love talking about what you are seeing. Some of my favorite moments have come from just asking, "What am I looking at?"

Make It a Flagstaff Day Trip

From Phoenix, Flagstaff is about two to two and a half hours north on I-17, so an afternoon and evening at Lowell makes a great day trip or the anchor for a weekend. The observatory is about a mile from historic downtown, so you can wander the shops and grab an early dinner before heading up Mars Hill.

If you have a second day, pair it with a morning at Walnut Canyon, Sunset Crater or Wupatki, or a drive up to the Arizona Snowbowl area for views of the San Francisco Peaks. Pack layers either way. Flagstaff weather can swing wildly between afternoon and night.

Lowell also hosts special events through the year, including its winter I Heart Pluto Festival around the anniversary of the discovery. Check the events calendar on lowell.edu for what is coming up.

Final Thoughts

Lowell Observatory is that rare place that works for everyone: little kids who want to see Saturn, history buffs who want to stand where Pluto was found, and anyone who simply wants to remember how big and beautiful the night sky is. Plan for an afternoon, stay for sunset, dress warm, and let Flagstaff's dark skies do the rest.