Bortle 2· Truly darkCertified reserveDesert

Big Bend Basin

United States · 29.25°, -103.25°

The darkest measured sky in the lower 48.

4.6(468)

Best night in range

Jun 16, 2026

2% cloud · 0% moon

92Sky score

SQM reading: 21.70mag/arcsec²
Naked-eye limit: 7.6mag
Clear nights: 268per year
Elevation: 1,140 m

The site

Big Bend protects over 3,200 km² along the Rio Grande with the least light pollution of any US national park unit. The Chisos Basin gives shelter from wind while keeping a clean southern horizon toward Mexico — useful for southern deep-sky targets that never clear the horizon further north.

Least light pollution of any US national park
Clean southern horizon down to −40° declination
Ranger-led star parties three nights a week

Ten-night forecast

Updated 6h ago

Sky Score combines cloud cover, transparency, seeing, humidity and lunar illumination against this site's Bortle class. Higher is better; anything above 82 is worth rearranging a calendar for.

Night	Moon	Cloud	Transparency	Seeing	Humidity	Sky score
SunJun 14	3%	45%	64%	57%	47%	67
MonJun 15	0%	25%	82%	86%	27%	83
TueJun 16Best	0%	2%	86%	85%	17%	92
WedJun 17	2%	50%	57%	50%	53%	63
ThuJun 18	6%	52%	52%	80%	52%	66
FriJun 19	12%	52%	64%	71%	50%	66
SatJun 20	20%	28%	72%	52%	30%	73
SunJun 21	29%	41%	57%	51%	39%	64
MonJun 22	39%	36%	72%	69%	34%	70
TueJun 23	50%	36%	63%	73%	39%	68

When to come

Share of nights that stay usable, month by month. The recommended window is March, April, October, November and December.

74%

72%

78%

80%

76%

70%

62%

60%

68%

80%

82%

78%

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Recommended windowShare of clear nights