Ontario, CA — light pollution & stargazing
Ontario, California has a light-pollution rating of about Bortle 8 — a city sky (very poor — city glow) — measured from VIIRS 2024 satellite night-lights at 59 nW/cm²/sr at the town center. The sky is bright enough to read by. Only the Moon, the planets, and the few brightest stars and clusters are visible — the constellations lose most of their fainter stars. The nearest genuinely darker skies are around Claremont, CA (about 5 mi away, Bortle 7). Tonight's Moon phase, cloud cover, and aurora odds load live below, computed in your browser. This is a satellite upward-radiance proxy for planning, not a survey-grade sky-brightness measurement.
Stargazing in Ontario tonight
- Estimated Bortle class
- 8 of 9
- VIIRS radiance (town center)
- 59 nW/cm²/sr
- Naked-eye limiting mag.
- 4.1–4.5
- Milky Way
- not visible
City sky. A satellite upward-radiance proxy for planning — not a survey-grade sky-brightness reading.
What you can see from Ontario
The sky is bright enough to read by. Only the Moon, the planets, and the few brightest stars and clusters are visible — the constellations lose most of their fainter stars.
Darker skies within reach
The nearest town in each darker class — your ladder from Ontario's sky toward truly dark skies.
| Town | State | Bortle | Sky | Drive |
|---|---|---|---|---|
| Claremont | CA | 7 | Suburban / urban transition | 5 mi |
| Chino Hills | CA | 6 | Bright suburban sky | 8 mi |
| Crestline | CA | 5 | Suburban sky | 24 mi |
| Agoura Hills | CA | 4 | Rural / suburban transition | 65 mi |
Frequently asked questions
- Can you see the Milky Way from Ontario, CA?
- Not really. At about Bortle 8 the Milky Way is not visible from Ontario — the sky is too light-polluted. The nearest genuinely dark skies are around Claremont, CA, about 5 mi away.
- How dark is the sky in Ontario?
- Ontario rates a city sky — about Bortle 8, with a naked-eye limiting magnitude around 4.1–4.5. That comes from a VIIRS satellite night-lights reading of 59 nW/cm²/sr at the town center. It is a satellite proxy for planning, not a survey-grade measurement.
- Where is the nearest dark sky to Ontario?
- The nearest town with genuinely darker skies is Claremont, CA — about 5 mi away at roughly Bortle 7. See the "darker skies within reach" list on this page for more options.
- Can I see the aurora from Ontario tonight?
- It depends on tonight's space weather. The live panel on this page reads the current NOAA aurora forecast for your latitude, along with cloud cover and the Moon — most U.S. locations only see aurora during strong geomagnetic storms.
The darkness rating is measured from VIIRS satellite night-lights at the town center and is a proxy for planning, not a survey-grade sky-brightness measurement — and the darkest skies are usually a short drive out of any town. Tonight's Moon, cloud, and aurora figures are live third-party forecasts that can change. See the methodology for sources and limits.
More in California
See every town's darkness rating in California, learn to read the Bortle scale, or check tonight's Moon phase.