How dark is the sky at Organ Pipe Cactus National Monument?

Modelled zenith brightness from the 2024 World Atlas of Artificial Night Sky Brightness puts Organ Pipe Cactus National Monument at about 21.75 mag/arcsec², roughly Bortle class 3. That is an approximation derived from satellite data, not a field measurement; it is certified by DarkSky International as an International Dark Sky Park.

How far is Organ Pipe Cactus National Monument from Tucson?

About 174.3 km in a straight line, heading west from Tucson. Using a 1.3 road-detour factor and staged average speeds that is roughly 226.6 km and 2.8 h of driving — an estimate, not a routed drive time.

When is the next moon-free dark window at Organ Pipe Cactus National Monument?

The next stretch of essentially moon-free dark hours runs Nov 2–15 (14 nights), computed from Moon phase and altitude with Skyfield and JPL DE440s. Cloud cannot be known that far ahead; the live seven-night forecast on this page shows real cloud cover once a window is close.

What is the clearest month at Organ Pipe Cactus National Monument?

Over 2021–2025, April (97%), June (97%), October (97%) had the highest share of nights with astronomical darkness that stayed clear (weighted cloud cover ≤ 20%); across the year it was 90%. ERA5 reanalysis via Open-Meteo — historical frequency, not a forecast.

United States · International Dark Sky Park

Stargazing at Organ Pipe Cactus National Monument

How dark this certified sky really is, how far it is from the nearest cities, a live seven-night forecast for the site itself, and the moon-free nights worth planning around. Official DarkSky International page ↗

Sky at the siteBortle ≈ 321.75 mag/arcsec² · 2024 atlas

From Tucson~2.8 h174.3 km straight-line · head west · estimated

Next moon-free windowNov 2–1514 nights · moon geometry only

How dark the sky really is at Organ Pipe Cactus National Monument

Modelled zenith brightness at the site's coordinates is 21.75 mag/arcsec², which maps to roughly Bortle 3 (what each level means). This is an approximation from the 2024 light-pollution atlas, not a field measurement — and it describes the single point DarkSky lists, not the darkest corner of the park.

A genuinely dark rural sky: the Milky Way shows real structure overhead, galaxies and nebulae are rewarding in binoculars and small telescopes, and only a faint glow near the horizon betrays the nearest towns. For most visitors this is the darkest sky they will ever observe under.

Getting to Organ Pipe Cactus National Monument

The nearest cities we publish guides for, with the direction to head and a rough drive estimate.

From Tucson
head west · 174.3 km straight-line · ≈226.6 km by road · ≈2.8 h · weekend trip
From Phoenix
head south · 179.2 km straight-line · ≈233 km by road · ≈2.9 h · weekend trip
From Flagstaff
head south · 375.8 km straight-line · ≈488.5 km by road · ≈5.6 h · weekend trip

Estimated from straight-line distance x a 1.3 road-detour factor and staged average speeds (40 km/h leaving town, 70 km/h regional, 95 km/h highway). It is a rough guide, not a routed drive time.

The next seven nights at Organ Pipe Cactus National Monument

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Plan the next 90 days at Organ Pipe Cactus National Monument

Moon-free dark windows are astronomy — computable years ahead. Cloud is not: beyond the 16-night forecast nobody knows the weather, and we won't pretend to. What five years of reanalysis can say is how often each month's nights actually stayed clear here.

Nov 2–1514 moon-free nights89% of November nights here stayed clear (2021–2025)
Dec 2–1413 moon-free nights78% of December nights here stayed clear (2021–2025)
Dec 31 – Jan 1314 moon-free nights78% of December nights here stayed clear (2021–2025)

Clear nights by month, 2021–2025

Jan84%
Feb84%
Mar85%
Apr97%
May96%
Jun97%
Jul88%
Aug92%
Sep91%
Oct97%
Nov89%
Dec78%

Clearest months historically: April (97%), June (97%), October (97%); across the year 90% of nights with astronomical darkness stayed clear.

"Clear" = weighted cloud cover (low 0.5 / mid 0.3 / high 0.2) ≤ 20% across the night's astronomical darkness. ERA5 reanalysis via Open-Meteo Archive, 2021–2025 (CC BY 4.0) — historical frequency, not a forecast. Once a window comes within 16 nights, the live forecast above takes over.

Put Organ Pipe Cactus National Monument's dark-sky nights on your calendar

Every month has a stretch of nights when the Moon leaves the dark hours at Organ Pipe Cactus National Monument essentially moon-free. Subscribe once and each window lands in your own calendar, about a year ahead — no account, no email.

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moon & darkness geometry only — cloud can't be known this far out; check the live forecast above when a window gets close

Questions people ask about Organ Pipe Cactus National Monument

How dark is the sky at Organ Pipe Cactus National Monument?: Modelled zenith brightness from the 2024 World Atlas of Artificial Night Sky Brightness puts Organ Pipe Cactus National Monument at about 21.75 mag/arcsec², roughly Bortle class 3. That is an approximation derived from satellite data, not a field measurement; it is certified by DarkSky International as an International Dark Sky Park.
How far is Organ Pipe Cactus National Monument from Tucson?: About 174.3 km in a straight line, heading west from Tucson. Using a 1.3 road-detour factor and staged average speeds that is roughly 226.6 km and 2.8 h of driving — an estimate, not a routed drive time.
When is the next moon-free dark window at Organ Pipe Cactus National Monument?: The next stretch of essentially moon-free dark hours runs Nov 2–15 (14 nights), computed from Moon phase and altitude with Skyfield and JPL DE440s. Cloud cannot be known that far ahead; the live seven-night forecast on this page shows real cloud cover once a window is close.
What is the clearest month at Organ Pipe Cactus National Monument?: Over 2021–2025, April (97%), June (97%), October (97%) had the highest share of nights with astronomical darkness that stayed clear (weighted cloud cover ≤ 20%); across the year it was 90%. ERA5 reanalysis via Open-Meteo — historical frequency, not a forecast.

Place name and coordinates: DarkSky International (reviewed 2026-07-15, data 2026-10-13). Light pollution: David Lorenz, World Atlas 2024 (EOG VIIRS, CC BY 4.0), approximate. Cloud: Open-Meteo.com (CC BY 4.0). Moon and darkness geometry: Skyfield + JPL DE440s, computed locally. Drive times are estimates, not routes.