In Southern California, we’ve got enough cloudless dark sky communities to spot meteor showers and a bright enough moon to hike at night. Plus, with all of these mountains bringing us to higher elevations, it's no wonder we find our gazes turning upwards.
Located at 5,715 feet above sea level, Mt. Wilson Observatory is one of the oldest and most historic gateways to space that’s been treasured by professional and amateur stargazers alike. With a long history as a research facility, it also houses two of the largest telescopes in the world that have been made exclusively available to the public.
Built by George Ellery Hale and John D. Hooker, these telescopes provided a way for humankind to try to understand the starry blanket that tucked them in every night. They also facilitated amazing discoveries in the sky above and in the universe as a whole.
Here are five ways that the Mount Wilson Institute has made the Mt. Wilson Observatory available for public education and enjoyment — and five of the best reasons to visit for the first time or return for another visit.
1. Observatory Guided TourA good starting point in your exploration of the Mt. Wilson Observatory campus is to be guided through the maze of passages that wind around the many telescopes of the facility. Mt. Wilson is probably best known for its 60-inch and 100-inch telescopes — both of which you’ll enter on a guided tour.
It's a marvel that either of them was even built. Decades before the Angeles Crest Highway, the only way to get to the top of Mount Wilson was via the Mount Wilson Toll Road, a 19th-century wagon road. While pack mules trudged up the mountainside with materials for the 60-inch, freight carriers heading up from Pasadena with big pieces of the 100-inch telescope dome building (to be reassembled at the top) couldn’t fit. The toll road had to be widened to 12 feet to accommodate them. That dome’s massive scale is evident when the guided tour takes you into the 100-inch dome, and you stand directly beneath its telescope.
For more than 50 years, Mt. Wilson maintained a reputation as a premier solar observatory — in fact, “Solar” was an original part of its name, and Hale was primarily a student of the sun. Three active solar towers — a 60-foot (operated by USC), a 150-foot (operated by UCLA), and the Snow Solar Telescope (the first permanent instrument on the mountain) — remain. Attendees of the weekend public tour usually go inside the 150-foot Solar Tower — which, for a half-century, was the largest instrument for studying the sun. Otherwise, free solar viewing through a portable 100 millimeter Lunt solar telescope is offered to the public through October on clear, sunny Saturdays and Sundays from 2 to 4 p.m. behind the Cosmic Café.
Docents lead two daily public walking tours of the observatory every Saturday and Sunday at 11:30 a.m. and 1 p.m. until December. Tickets for ages six and up are available at the Cosmic Café, where the tour departs.
2. 60-inch Telescope Stargazing
Of the many adventures that you’ll have in Southern California, only a few can really alter your perception or change your life — making them a "must-do." One of them is a nighttime star party at Mt. Wilson Observatory, where the night sky and the heavens are revealed one sliver at a time, one squint through the eyepiece at a time.
During summer months, the evenings are short, with long hours of daylight — so, as you drive up the mountain, half the forest is bathed in amber glow, and the other half is darkened in dusky shadows. When you arrive, you’re ushered through a locked gate, and the magic soon begins.
Observatory founder George Ellery Hale completed the 60-inch telescope in 1908 with funding from Andrew Carnegie. The telescope features coudé foci instrumentation, which was later used on the 100-inch. In fact, astronomers and engineers first understood many of the problems of telescope design while working on the 60-inch — and figured out the solutions, which would then be applied to all subsequent telescopes that followed.
The world’s largest operational telescope at the time, it measured the size of the Milky Way and our position in the galaxy. It was also able to photograph Halley’s Comet — a historic feat in 1910. During a modern-day nighttime observation, you might spot planets like Mars, a waxing gibbous moon, blue-ringed nebulae, and even a globular cluster through the aperture in the 58-foot dome. But perhaps the most spellbinding, spectacular vision is Saturn with its rings, surrounded by its moons, in sharp definition.
You’re merely observing what’s already known, but it’s so much more than you could ever see through bedroom telescopes and amateur astronomy club equipment. In fact, it would only be outdone in 1917, when Hale went on to complete the Mt. Wilson 100-inch telescope.
Occasionally, public stargazing nights offer individual tickets — but the most common way is to schedule a half-night or full night for a group of up to 25 people. Bookings are available from the beginning of March to the end of November. A full calendar of availability is available online.
3. 100-inch Telescope Stargazing
After 98 years of purely professional use, Mount Wilson Observatory finally opened the doors of the 100-Inch Hooker telescope for public nighttime viewing in 2015. This National Mechanical Engineering Landmark is so huge, you’ll pass three landings as you climb the stairs to the top — and then, once you're under the dome, climb one more level to get to the Hooker telescope control center, which is more or less unchanged from the days of astronomer Edwin Powell Hubble. At the helm, Hubble changed the way we looked at the universe and became known as a "pioneer of distant stars” — establishing once and for all the mind-blowing premise that the universe was (and is) expanding. And that expansion is accelerating over time.
Using the 100-inch telescope helped us confirm what we’d suspected thanks to observations from the 60-inch: The Milky Way is not the only galaxy in the cosmos. And, using a powerful telescope to gaze into the night sky, we're able to actually witness, document and measure these extragalactic worlds, hundreds or even thousands of light-years away. Case in point: One of the points on the Northern Cross, the binary star Albireo, can be visible through the scope, though it’s 430 light-years away from Earth. You'll find it located at the beak of Cygnus, the swan constellation. What looks like one white dot with the naked eye is actually two stars — one gold and one blue, several lifetimes apart from each other.
It may sound hard to believe — until you look through a telescope like that yourself and view those very objects in the sky with even greater clarity than through the 60-inch. You might see the red gaseous rings and double stars and dwarf planets and moons — objects that look like white dots to the naked eye (or even through binoculars) but explode into a variety of shapes and colors and rings and halos. A twinkling sky might actually be swirling. And because so much of what's out there is so far away and it takes so long for the light to reach our eyeballs, it's possible that whatever objects you can see through that telescope might not actually exist anymore.
Individual tickets are occasionally available for public stargazing nights. Or, schedule a half-night or full night for a group of up to 20 people from the beginning of April to the beginning of November by booking online.
4. Engineering Tour
On a few select weekends, stargazers are in for a special treat — because the Mount Wilson Institute conducts special behind-the-scenes tours of the 60-inch and 100-inch telescopes, machine shop and historic powerhouse. On the engineering tours, volunteer engineers — like Bill Leflang, who’ve spent years helping to maintain the telescopes — lead small groups through all the mechanical, optical, and electrical details of these historic instruments. You won’t see any stars in the sky, as these are daytime tours without sky observation through the telescope — but you’ll have stars in your eyes as you marvel at the machinery and all the inner workings.
In the 60-inch, you’ll see original levers, outdated control panels, an array of tools, and the huge gears that help move the telescope above (as well as its oil reservoir). You’ll even pass by Hubble's locker where he once stored his lunch! And in the 100-inch, you’ll stand beneath the chair where Hubble measured the expansion of the universe. From the control console, your docent engineer will rotate the dome (whose wheels run on railroad tracks!) and demonstrate different speeds of “slewing” the telescope (generally ranging from slow to slower and slowest).
Get ready for grease galore as you cram into the smaller mechanical area beneath the telescopes and learn how the electrical control systems have been modernized over the last 102 years — especially evident when you see the original electrical panel of the 100-inch, some of which is still in use (and still “hot”).
After lunch, you’ll visit the Observatory’s original powerhouse for a demonstration of its 50 HP Fairbanks-Morse Type RE engine/generator (circa 1911) by brothers Ken and Larry Evans. This twin-cylinder gas-fueled engine — once nicknamed "Big Ben" by early engineers — helped generate 40 kilowatts of power at 125 volts direct current. The Evans brothers refurbished it in 1999 and got it running for the first time in 30 years in 2000. It’s mind-blowing to see the rotating crankshaft, moving piston, pumping gasoline, and operating cylinders — all helping this magnificent machinery operate at 300 rpm.
The machine shop and powerhouse are not open to the general public and can only be accessed via the Engineering Tour, offered by Mt. Wilson Institute on select dates. Tickets for ages 12 and up are available for purchase online.
5. Self-Guided TourWhile you’re at Mt. Wilson, stop by the Museum’s exhibit space for historical photos and other materials from the observatory’s research programs, including a 1920s-era scale model of the observatory. Built in 1936, you can visit free of charge. You’ll find it across from the 150-foot Solar Tower, between the paved access road and the Rim Trail.
On the ground level of the 100-inch, you’ll find another Astronomical Museum — this one containing wheels once used to rotate the 100-inch dome as well as telescope mirror polishing machines and disks, an aluminizing tank and other optical equipment.
Across from the 100-inch dome, you can visit the interferometry exhibit, whose displays describe the operation and early results of the six telescopes that comprise the CHARA (Center for High Angular Resolution Astronomy) Array (operated by Georgia State University). The exhibit hall also includes the world’s first stellar interferometer, the direct ancestor of modern interferometers such as CHARA and ISI. It could measure the diameters of large stars (like the red supergiant star, Betelgeuse), and between 1920 and 1930, it was installed periodically atop the 100-inch telescope.
The observatory grounds are open to visitors every day from 10 a.m. to 5 p.m. through the spring, summer and fall. During the winter months (December through March), the grounds close at 4:00 p.m. All parked vehicles must display a U.S. Forest Service Adventure Pass, which can be purchased onsite at the Cosmic Café during its weekend-only open hours, 9 a.m. to 5 p.m. March 31 through December 2.
Mt. Wilson's "Sunday Afternoon Concerts in the Dome" series runs monthly, May through October. Check the online calendar for the upcoming schedule of musical performances, plus a monthly lecture series.
Top Image: NASA Spitzer Space Telescope offers a fresh, infrared view of the frenzied scene at the center of our Milky Way, revealing what lies behind the dust.| NASA/JPL-Caltech
Updated: August 5, 2021