Entry No. 210 — the Denver file — filed under: after-dark
Sommers-Bausch Observatory Open House Nights
On CU Boulder's main campus next to Fiske Planetarium, this working teaching observatory throws open its rooftop observing deck on clear Friday nights, free of charge. You queue at the eyepiece of two 20-inch PlaneWave telescopes aimed at the Moon, planets, nebulae and galaxies, with live camera feeds on big screens for anyone who can't manage the step ladder. Because they only open under clear skies, they post a go/no-go status on Facebook and Instagram and by phone (303-492-2020) in the hour before start time. Sessions run loose, one to three hours, depending on the weather and the crowd.
The story
In 1949, Mayme Sommers bequeathed $49,054 to the University of Colorado in memory of her late husband Elmer, while optics firm Bausch & Lomb donated a 1912 refractor formerly owned by company director Carl Bausch. CU wrapped the resulting 1953 observatory in rural Italian-style sandstone to match the rest of campus. But while most academic observatories lock their research gear behind security passes, CU's Department of Astrophysical and Planetary Sciences keeps this rooftop observation deck open to anyone who wanders up on a clear Friday.
The original glass has long since been upgraded to high-end optical systems: two 20-inch PlaneWave Corrected Dall-Kirkham telescopes (nicknamed Apollo and Artemis) sit on the roof deck alongside a 24-inch Boller & Chivens reflector. Rather than hiding behind esoteric jargon, the astronomy professors, lab staff, and graduate students running the deck point the high-powered assemblies at lunar craters, Saturn's rings, or distant star clusters, explaining exactly what you're looking at through the eyepiece.
Because mountain weather changes fast and lower views to the southeast catch glow from the Denver metro area, staff aim the glass high into the darker skies above the Flatirons. If climbing the short stepladders to the eyepiece isn't an option, live video feeds stream from the cameras directly to big screens on deck. It is a rare piece of working university infrastructure handed over to the public completely free of charge.
What it's like
Before you head out, check for weather cancellations—if cloud cover rolls over the Flatirons, the open house gets scrubbed, so confirm status on Instagram, Facebook, or by calling 303-492-2020 after 7:45 p.m. On clear nights, you'll walk onto CU's main campus next to Fiske Planetarium and join a loose crowd of students, locals, and families on the roof. Lines at the eyepieces move fast as visitors trade turns on the stepladders. Dress significantly warmer than you think you need to for standing still on an exposed rooftop at night, or stick to the big-screen video feeds if you prefer to stay on ground level.
The move: Check the clear-sky status, then spend a free Friday night trading turns at the 20-inch telescope on the open rooftop deck.
📍 Before you go Friday-night open houses only happen on clear nights while CU is in session; summer start is 9pm. Call after 7:45pm for status. Free.
- 📍 Boulder
- 💸 $
- ⚡ Low-key
- 🌗 Outdoors
Where: 2010 Colorado Ave, Boulder, CO 80305
Hours: Added 2026-06-23 — confirm current hours before you go.
⚠ Seasonal or scheduled — always check before you go.
Pair it with
- Fiske Planetarium Laser & Liquid Sky Shows — Sit through cosmic dome projections inside Fiske next door before stepping outside to peer through the observatory's 20-inch glass.
- License No. 1 — Trade the cold rooftop air and stargazing for a post-observation cocktail in the basement speakeasy beneath the Hotel Boulderado.
- The Lighthouse Bookstore — Pair looking at deep-sky objects through research telescopes with browsing two floors of metaphysical texts down on Pearl Street.
- Eldorado Springs Pool & Artesian Spring — Combine gazing light-years into the night sky with a day dip in 6,000-year-old artesian spring water five miles south in Eldorado Canyon.
Good to know
How much does it cost to attend?
Admission is completely free, with no tickets or reservations required.
When do open houses take place?
They run on clear Friday evenings while CU Boulder classes are in session (during fall, spring, and summer terms). Start times vary by season with sunset—usually 8:00 p.m. in fall/spring and 9:00 p.m. during summer.
How do I check if an open house is happening?
Because open houses depend on clear weather, SBO posts a go/no-go status on Facebook and Instagram, or you can call 303-492-2020 after 7:45 p.m. on Friday night.
Can I view the stars if I can't climb a stepladder?
Yes. Live video feeds from the telescope cameras stream directly onto big screens on deck so everyone can view targets without climbing.
Where is the observatory located on campus?
It is located at 2010 Colorado Ave on CU Boulder's main campus, right next to Fiske Planetarium.
Plan a visit & invite your people →
Further reading: colorado.edu · Wikipedia · Reddit
last checked: 2026-06-23