Rancho Cucamonga Stargazing & Astronomy Report
Light pollution and stargazing locations near Rancho Cucamonga
- City
- Rancho Cucamonga
- Country
- United States
- Latitude
- 34.1064
- Longitude
- -117.5931
Key Sky Quality Metrics
- SQM (mag/arcsec²)
- 17.88
- Bortle class
- Class 9 (Class 9)
- Darkness Quotient
- 22%
- Dataset
- May 2026
Inner city sky
Rancho Cucamonga: The Practical Verdict
Rancho Cucamonga, a small city in California, faces high light pollution challenges typical of suburban areas near major urban centres. The overall sky quality here is severely impacted by the urban brightness, making it a difficult environment for astronomical observation.
The Milky Way remains invisible from Rancho Cucamonga's bright skies. For observation, you are limited to solar system targets such as the Moon and planets, bright stars, and double stars, with some imaging potential using narrowband filters. Serious deep-sky observing, particularly broadband galaxies and faint nebulae, should be avoided due to the pervasive light pollution.
For those seeking better sky quality for deeper stargazing, Los Angeles County, about 160 km to the south-south-west, offers a significant improvement with its Bortle 3 skies. This trip is worthwhile for those aiming for darker skies and enhances your potential for serious observation work.
At a Glance
- Overall
- Severe urban sky - This is a severely light-polluted urban sky. Only the Moon, planets, bright stars, and a few specialist targets remain practical.
- Milky Way
- Not visible - The Milky Way is not visible from this sky.
- Best targets from here
- Moon, planets, bright stars, double stars, solar system events, narrowband imaging only with care
- Do not prioritise
- visual deep-sky observing, broadband galaxies, reflection nebulae, widefield Milky Way
- Best nearby upgrade
- Los Angeles County, California sits about 158 km south south west and reaches Bortle 3, roughly 32x darker.
- Good dark window
- Rancho Cucamonga's longest dark windows fall in December and January, with the shortest nights around June and July. Plan deep-sky sessions around the autumn and winter months for the best combination of long nights and true astronomical darkness.
Frequently Asked Questions
Can you see the Milky Way from Rancho Cucamonga?
No. Rancho Cucamonga is a Bortle Class 9 sky with SQM 17.88, so the Milky Way is not visible from the city. For Milky Way photography, look for a Bortle 4 or darker site.
What Bortle class is Rancho Cucamonga?
Rancho Cucamonga is Bortle Class 9 (SQM 17.88), a severe urban sky for astronomy.
Is Rancho Cucamonga good for stargazing?
Not for serious deep-sky observing. Rancho Cucamonga is a severe urban sky where the Moon, planets, and a handful of bright targets are the realistic options from the city itself.
Is Rancho Cucamonga good for astrophotography?
Broadband deep-sky imaging is heavily compromised from Rancho Cucamonga and a Bortle 4 or darker site is strongly recommended. Even narrowband imaging is difficult from Rancho Cucamonga without careful processing.
What can you observe from Rancho Cucamonga?
Primary targets from Rancho Cucamonga include Moon, planets, bright stars, double stars, solar system events. Targets such as visual deep-sky observing, broadband galaxies, reflection nebulae are not realistic from this sky.
Where are darker skies near Rancho Cucamonga?
The closest meaningfully darker mapped site is Kruse Road, California, about 25 km north north east of Rancho Cucamonga, reaching Bortle 6.
When is the sky darkest in Rancho Cucamonga?
The sky over Rancho Cucamonga is darkest around January, December.
Is light pollution in Rancho Cucamonga getting better or worse?
Long-term light pollution over Rancho Cucamonga has been broadly stable across the available measurements.
north - good
No noticeable light pollution to the north. The sky in this direction is dark to the horizon.
north-north-east - good
The north-north-east sky is dark to the horizon. Faint targets are accessible at all elevations here.
north-east - fair
A trace of skyglow near the north-east horizon. Stars are clear throughout this direction except very close to the ground.
east-north-east - marginal
Noticeable glow on the east-north-east horizon. Stars below about 20 degrees in this direction are dimmed.
east - poor
Heavy light pollution to the east. The lower 30 degrees of sky in this direction are unusable for faint targets.
east-south-east - poor
The lower east-south-east sky is heavily light-polluted. Only the brightest stars stand out near the horizon.
south-east - marginal
The south-east lower sky is measurably brighter than the darker quarters. Limit faint work to above about 20 degrees here.
south-south-east - marginal
Noticeable glow on the south-south-east horizon. Stars below about 20 degrees in this direction are dimmed.
south - poor
The south horizon shows a strong orange-white glow. Star counts drop sharply below about 25 degrees here.
south-south-west - poor
Heavy light pollution to the south-south-west. The lower 30 degrees of sky in this direction are unusable for faint targets.
south-west - poor
Strong skyglow on the south-west horizon. Stars below about 30 degrees in this direction are largely lost.
west-south-west - poor
Heavy light pollution to the west-south-west. The lower 30 degrees of sky in this direction are unusable for faint targets.
west - marginal
A diffuse glow sits on the west horizon. Faint objects below 20 degrees in this direction are compromised.
west-north-west - fair
A faint diffuse glow on the west-north-west horizon. Stars are visible to low elevation, with minor losses near the ground.
north-west - fair
The north-west sky is broadly dark with a small amount of glow at the horizon. Most objects in this direction are accessible.
north-north-west - good
Dark sky in the north-north-west direction with no obvious skyglow. Suitable for faint-object work at low elevation.
zenith - poor
The zenith is bright enough to be obvious without dark adaptation. The Milky Way is not visible.
-
Angeles Crest Highway, California
- Direction
- NNW
- Distance (km)
- 31.6
- SQM
- 20.18
- Bortle
- 6
-
Kruse Road, California
- Direction
- NNE
- Distance (km)
- 24.8
- SQM
- 19.67
- Bortle
- 6
-
El Rancho Escondido Road, California
- Direction
- SW
- Distance (km)
- 112.6
- SQM
- 20.87
- Bortle
- 4
-
Los Angeles County, California
- Direction
- SSW
- Distance (km)
- 157.5
- SQM
- 21.63
- Bortle
- 3
-
De Luz Truck Trail, California
- Direction
- SSE
- Distance (km)
- 75.8
- SQM
- 19.53
- Bortle
- 7