Free Observatory Nights in California

More people have put an eye to the 12-inch Zeiss refractor on the roof of Griffith Observatory than to any other telescope on Earth — more than seven million since 1935, more than saw Halley’s Comet or Hale-Bopp through any single instrument anywhere. It sits in a dome above Los Angeles, points at the Moon and the planets over one of the most light-polluted basins in the country, and on any clear evening the Observatory is open you can walk up the ladder and take your turn for nothing. That is the whole idea of this page.

Most stargazing guides, ours included, tell you to drive: somewhere the sky is actually dark. That advice is right for the Milky Way. It is wrong for the planets and the Moon, which barely notice a city’s glow and look astonishing through a big telescope from the middle of one. California has six observatories that open their domes to the public on a regular schedule for free — run by a city, three colleges, a public library and some of the oldest amateur astronomy clubs in the West — spread from the Los Angeles hills to the East Bay, the Salinas Valley, the Sierra foothills and the desert. My own telescope is a 10-inch. The smallest instrument on this list is a 14-inch; the biggest gathers about thirteen times the light mine does. Here is where they are, which night each one opens, and how not to waste the drive.

Griffith Observatory, Los Angeles: the Zeiss 12-inch, free every clear night

Griffith Observatory charges nothing to walk in the door — only the planetarium show needs a ticket — and nothing to look through its telescopes. The headline instrument is the 12-inch Zeiss refractor in the rooftop dome on the east end, a 16-foot tube that collects its light through a foot-wide glass lens. Free public viewing runs each evening the building is open and the sky is clear, usually starting around 7:00 pm with the lines closing at 9:30. The building is closed Mondays. On a clear night the demonstrators pass roughly 600 people through that one eyepiece.

Once a month the Observatory also hosts a free public star party on the front lawn, where volunteers from the Los Angeles Astronomical Society, the Sidewalk Astronomers and The Planetary Society set up dozens of telescopes and a solar scope for daytime viewing of the Sun. If you are choosing a night, choose one when Saturn or Jupiter is up: a 12-inch on a bright planet shrugs off the city, where a faint galaxy from that rooftop is a lost cause. It is the single best free hour of astronomy in Southern California.

Chabot Space & Science Center, Oakland: three historic telescopes, Friday and Saturday

Up in the hills above Oakland, the Chabot Space & Science Center opens its observatory deck to the public every Friday and Saturday night, 7:30 to 10:30 pm, weather permitting — and that viewing is free, no museum ticket required. Three domes hold three named telescopes with real history: Leah, an 8-inch refractor from 1883; Rachel, a 20-inch refractor from 1916 and one of the largest refractors regularly open to the public in the country; and Nellie, a 36-inch reflector installed in 2003. Nellie’s mirror is the biggest eyepiece on this page, gathering about thirteen times the light of my 10-inch.

Eastbay Astronomical Society volunteers run the deck and answer questions. If the humidity is very high or it is cloudy the telescopes may stand down, but the domes still open so you can see the instruments; only rain closes the plaza outright. The address is 10000 Skyline Boulevard, and the drive up through Redwood Regional Park is part of the evening.

Foothill Observatory, Los Altos Hills: a 16-inch every clear Friday

On the campus of Foothill College in Los Altos Hills, the Foothill Observatory is owned and run jointly by the college and the Peninsula Astronomical Society, a Silicon Valley club that has been showing the public the sky for decades. Its dome holds a computer-controlled 16-inch Schmidt-Cassegrain, and the PAS opens it for free public viewing every clear Friday night, 9:00 to about 11:00 pm, plus safe solar viewing on clear Saturday mornings. No reservation — just come by; parking on campus is $3 from the machines in the lot.

One habit worth building: the club runs a webcam and posts the go/no-go, so check the site before you leave, because a Peninsula marine layer can close the dome on a night that looked fine from your driveway. The observatory shuts when it is cloudy, no exceptions.

Fremont Peak Observatory, San Juan Bautista: a 30-inch under a real dark sky

The one site on this list where the sky itself is dark. The Fremont Peak Observatory sits at 2,700 feet in Fremont Peak State Park, up eleven winding miles of San Juan Canyon Road from San Juan Bautista, and houses the 30-inch “Challenger” Newtonian, a telescope that gathers nine times the light of mine. The Fremont Peak Observatory Association runs free public programs on Saturday evenings from spring through fall — roughly April to October — starting around dusk and, when it is dark enough, inviting the public to observe through the 30-inch and members’ telescopes until at least midnight.

Programs are free; the state park charges $6 per vehicle for day use. No reservation is needed for individuals, though groups over ten should email ahead. Two warnings the club makes itself: the schedule that Apple and Google auto-fill is wrong, so read the dates on the FPOA schedule page; and the weather on the peak is often nothing like the weather down in Salinas, so check the program status the day of. When it is clear up there, this is the one where you will see the faint deep-sky objects the city sites can only hint at.

Community Observatory, Placerville: two reflectors and a sky theater, Fridays and Saturdays

In the Sierra foothills east of Sacramento, the Community Observatory at Folsom Lake College’s El Dorado Center runs two domes — a 17-inch and a 14-inch reflector — plus an outdoor “sky theater” amphitheater where docents give a guided tour of the naked-eye sky. It is open Friday and Saturday nights year-round (summer 9:00 to 11:00 pm, winter 7:30 to 9:30 pm; closed Sunday through Thursday), and admission is free, with campus parking at $2.

No reservation is required, and the observatory announces any weather closure by 3 pm on the day, so check the calendar before the drive up Campus Drive to Placerville. The sky-theater tour makes this a good one for a family that is new to all of it: you learn the constellations outside first, then look through the domes.

Rancho Mirage Library & Observatory: the desert’s free public dome

Greater Palm Springs has a genuine surprise: the Rancho Mirage Library & Observatory is a public library that also runs a rotating-dome observatory with a research-grade 0.7-metre (27.6-inch) PlaneWave CDK 700, and its drop-in stargazing nights are free. Its “OPENights” sessions run most Thursdays and Saturdays through the year, no registration — you queue and you are guaranteed a look as long as you are in line by the end time — delivering magnifications from 30x up past 1,000x on the planets, nebulae and star clusters, weather permitting.

Some of the deeper programs (guided stargazing and the education sessions) take advance sign-ups through the library’s calendar, but the basic public nights do not. The observatory is at 71-100 Highway 111 in Rancho Mirage, it is fully accessible, and it is the rare desert-sky telescope you can reach without a dirt road or a club membership.

What a public observatory night is actually like

None of these is a planetarium show. You are visiting a working telescope run by staff or volunteers who are there because they like showing people the sky, and the evening has a rhythm worth knowing before you arrive.

• You’ll wait, then look, then wait again. A dome holds a dozen or so people and the telescope shows one object at a time. Expect a few minutes at the eyepiece per object, and ask the operator what’s next; they love that question.
• Red light only. Every observatory here runs on red light after dark to protect night vision. Bring a red flashlight (our red flashlight guide has picks from $10) and dim your phone before you walk in. A white screen in a dark dome is the one way to annoy everyone in it.
• Dress for outside, even indoors. Domes and roll-off roofs are unheated by design, so the air inside matches the telescope. Bay Area and foothill nights get cold fast after sunset, and the desert swings hard once the sun is down.
• It cancels for cloud, and that’s a feature. A telescope through overcast shows nothing, so every site above decides that afternoon or at dusk. Check the hotline, webcam or calendar after about 4 pm before you leave the house.
• The Moon is a target, not an enemy. Dark-sky travel wants a new Moon. Observatory nights are the opposite: a first-quarter Moon through a big telescope is the best thing on the menu, craters and mountains lit from the side. Our Moon-observing guide explains why the terminator, not the full Moon, is where the detail lives.

What you’ll see, by season

The planets set the calendar. Saturn is the reason most people say “oh” at the eyepiece, and it is an evening object from late summer through the end of the year; our Saturn guide has the dates. Jupiter follows it into the evening sky through autumn and winter, its four big moons rearranged every night. Summer brings the Ring Nebula and the great globular cluster in Hercules; autumn the Andromeda Galaxy, a soft oval from a city dome but the light of a trillion suns, two and a half million years old, landing in your eye; winter the Orion Nebula, spectacular in any aperture and stunning in a 20- or 36-inch. The Moon is up about half the nights of any month, and through these telescopes it never gets old. From the dark peak at Fremont, add the faint galaxies and nebulae the city sites cannot reach.

If the eyepiece gets you

It does that. Half the people who own a telescope bought one after a night like this. The honest next step isn’t a 30-inch; it’s the beginner’s guide to learning the sky with your eyes, then a pair of astronomy binoculars or one of our beginner telescope picks, most of which cost less than a nice dinner out. When you want the sky itself and not just the objects, California has some of the best national parks for stargazing in the country. And if you are reading this from the other coast, the New Jersey list does the same thing near New York. Do the free night first. Zero dollars and someone else’s 20-inch is the best deal in astronomy.