Free Observatory Nights in Massachusetts

The oldest large telescope in America that you can still look through sits on a hill behind Harvard, off Garden Street in Cambridge: a 15-inch brass refractor finished in 1847 that was the biggest telescope in the country for its first twenty years and took some of the first photographs of a star. On the right evening the Harvard College Observatory opens its doors, gives a short talk, and walks you up to the roof to put your eye to a telescope for nothing. That is the idea behind this page, and Massachusetts does it better than almost anywhere.

Most stargazing guides, ours included, tell you to drive somewhere the sky is actually dark. That advice is right for the Milky Way and wrong for the Moon and the planets, which barely notice a city’s glow and look astonishing through a big telescope from the middle of one. That is lucky, because Massachusetts is a small, cloudy, well-lit state — and it has packed an unusual number of public observatories into it: a museum on a Boston rooftop, two university decks, and two 19th-century college refractors out in the Pioneer Valley, most of them free and open on a set night. My own telescope is a 10-inch. The smallest instrument on this list is a 6-inch and the biggest gathers about nine times the light mine does. Here is where they are, which night each one opens, and how not to waste the trip.

Harvard College Observatory, Cambridge: the historic Great Refractor and Observatory Nights

The Harvard-Smithsonian Center for Astrophysics runs a free public series called Observatory Nights at 60 Garden Street, the home of the Harvard College Observatory since 1847. Each one pairs a short, non-technical talk by a working astronomer with telescope observing from the observatory roof afterward, weather permitting. Admission is free. In the dome sits the Great Refractor, a 15-inch lens telescope installed in 1847 that was the largest in the United States for two decades and, in 1850, took the first daguerreotype of a star; the rooftop telescopes are what you actually observe through on the night.

These are the one entry on this list I would not turn up to on a whim. They run on selected evenings through the year, not every week, and they are popular enough to fill up — so read the current schedule and grab a free seat from the observatory’s own page before you go. If a clear evening lines up with a scheduled night, it is the best free hour of astronomy in greater Boston, history and all.

Museum of Science, Boston: a free rooftop dome every clear Friday

On the roof of the Museum of Science parking garage, above the Charles River between Boston and Cambridge, the Gilliland Observatory opens for free public stargazing — a program the museum calls Astronomy After Hours — on Friday evenings, roughly 8:30 to 10:00 pm, weather permitting, funded by the Lowell Institute so that it costs nothing and needs no museum ticket. The dome holds three telescopes, the main one a computer-driven Celestron CGE 1100, an 11-inch Schmidt-Cassegrain that shows the Moon and planets in fine detail even over one of the brightest skies in New England.

The season runs about March through November, and because a New England Friday can cloud over by dusk, the museum posts a go or no-go on its observatory hotline (617-589-0267) by around 5:30 pm that day. On a cloudy night the staff still open up for a look at the instruments and some astronomy activities. It is the easiest big-telescope look in the city — a subway ride, no reservation, no charge.

Boston University: the Coit Observatory open night, most Wednesdays

Boston University’s astronomy department runs a free Public Open Night at the Judson B. Coit Observatory, on the roof at 725 Commonwealth Avenue, on most Wednesday evenings year-round — starting at 7:30 pm in the colder months and 8:30 pm in spring and summer, running about an hour. The observation deck is lined with telescopes, the largest in the 14-inch range, and graduate-student astronomers run them and answer questions. The whole thing is free.

The one wrinkle: it is ticketed. Free tickets, limited to five per person, are released on the department’s Eventbrite page on Thursday mornings around 11 am for the following week, and they go quickly. The deck is reached only by stairs (the fifth floor of the building) and unaccompanied minors are not admitted. Clouds cancel it, so check the recorded line at 617-353-2630 within a couple of hours of the start time before you head over.

Whitin Observatory, Wellesley: two historic refractors, about once a month

Fifteen miles west of Boston, Wellesley College keeps one of the loveliest small observatories in the state. The Whitin Observatory holds a historic 12-inch refractor and a smaller 6-inch, both more than a century old, and the student-run astronomy club hosts a free public night about once a month during the academic semesters. Unusually, the public nights happen regardless of weather: if it is clear you look through the telescopes, and if it is cloudy you still get the tour and the talks and a walk around the domes.

No reservation is needed; visitors park in the Davis Parking Facility on Central Street and walk over, and a few steps lead up to each telescope. It is a good one for a first visit, because the evening is built around explaining the sky, not just pointing at it.

Orchard Hill Observatory, UMass Amherst: a 16-inch every Thursday

Out in the Pioneer Valley, the University of Massachusetts Amherst opens its Orchard Hill Observatory for free public viewing every Thursday evening, 7:30 to 9:30 pm, weather permitting. It sits on the highest point on campus and houses a 16-inch Cassegrain reflector that has been the department’s public telescope since 1976, gathering about two and a half times the light of a good beginner scope.

Because the hilltop can cloud over on its own schedule, the observatory asks you to call its status line (413-577-4166) after 7:00 pm to confirm the sky and the equipment are cooperating before the drive up. When it is clear, a hilltop away from the worst of the valley’s lights is a real step up on what you can see from town.

Wilder Observatory, Amherst: an 18-inch Alvan Clark refractor on clear Saturdays

A few miles from UMass, Amherst College keeps the biggest lens on this page. Wilder Observatory is free and open to everyone at 9:00 pm every clear Saturday, April through October, and its dome holds an 18-inch refractor built by Alvan Clark & Sons — the same 19th-century Massachusetts firm that ground the lenses for the largest refractors ever made. Eighteen inches of glass is one of the largest refractors regularly open to the public anywhere, and through it, depending on the night, you can see the Moon, the planets, double stars, clusters, nebulae and galaxies.

It runs only in the clear-weather half of the year and only on Saturdays, so it rewards a little planning — but a look through a great classical refractor is a different experience from a modern reflector, sharp and high-contrast, and this is a free chance at one of the finest in the region.

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, so expect a couple of minutes at the eyepiece per target. 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 sure way to annoy everyone in it.
• Dress colder than the day. Domes and roll-off roofs are unheated by design so the air inside matches the telescope, and a New England evening drops fast after sunset. Bring the jacket you think you won’t need.
• It cancels for cloud, and that’s a feature. A telescope aimed through overcast shows nothing, so every site above decides that afternoon or at dusk. Check the hotline, ticket page or status line after about 4 pm before you leave.
• The Moon is a target, not an enemy. Dark-sky trips want a new Moon; observatory nights are the opposite. A first-quarter Moon through a big telescope is the best thing on the menu, its 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” out loud 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 autumn and winter sky, its four bright moons rearranged every night. Summer brings the Ring Nebula and the great globular cluster in Hercules; autumn the Andromeda Galaxy, a soft oval even from a city dome but the light of a trillion suns that left two and a half million years ago; winter the Orion Nebula, spectacular in any aperture and stunning through the 16- and 18-inch scopes out in Amherst. The Moon is up about half the nights of any month, and through these telescopes it never gets old.

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 an 18-inch refractor; 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. If you are reading this from another state, the New Jersey list does the same thing near New York and the California list covers the West Coast, from Griffith to a 36-inch in Oakland. Do the free night first. Zero dollars and someone else’s telescope is the best deal in astronomy.