How dark is the sky at Mayo Dark Sky Park?

Modelled zenith brightness from the 2024 World Atlas of Artificial Night Sky Brightness puts Mayo Dark Sky Park at about 21.87 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 Mayo Dark Sky Park from Belfast?

About 260.5 km in a straight line, heading west from Belfast. Using a 1.3 road-detour factor and staged average speeds that is roughly 338.7 km and 4 h of driving — an estimate, not a routed drive time.

When is the next moon-free dark window at Mayo Dark Sky Park?

The next stretch of essentially moon-free dark hours runs Nov 3–15 (13 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 Mayo Dark Sky Park?

Over 2021–2025, April (33%), May (31%), June (20%) had the highest share of nights with astronomical darkness that stayed clear (weighted cloud cover ≤ 20%); across the year it was 16%. ERA5 reanalysis via Open-Meteo — historical frequency, not a forecast.

Ireland · International Dark Sky Park

Stargazing at Mayo Dark Sky Park

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 ≈ 321.87 mag/arcsec² · 2024 atlas

From Belfast~4 h260.5 km straight-line · head west · estimated

Next moon-free windowNov 3–1513 nights · moon geometry only

How dark the sky really is at Mayo Dark Sky Park

Modelled zenith brightness at the site's coordinates is 21.87 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 Mayo Dark Sky Park

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

From Belfast
head west · 260.5 km straight-line · ≈338.7 km by road · ≈4 h · weekend trip
From Glasgow
head south-west · 410.3 km straight-line · ≈533.4 km by road · ≈6.1 h · weekend trip
From Edinburgh
head south-west · 474.1 km straight-line · ≈616.3 km by road · ≈6.9 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 Mayo Dark Sky Park

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Plan the next 90 days at Mayo Dark Sky Park

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 3–1513 moon-free nights4% of November nights here stayed clear (2021–2025)
Dec 2–1514 moon-free nights9% of December nights here stayed clear (2021–2025)
Dec 31 – Jan 1314 moon-free nights9% of December nights here stayed clear (2021–2025)

Clear nights by month, 2021–2025

Jan9%
Feb9%
Mar18%
Apr33%
May31%
Jun20%
Jul12%
Aug18%
Sep17%
Oct8%
Nov4%
Dec9%

Clearest months historically: April (33%), May (31%), June (20%); across the year 16% 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 Mayo Dark Sky Park's dark-sky nights on your calendar

Every month has a stretch of nights when the Moon leaves the dark hours at Mayo Dark Sky Park 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 Mayo Dark Sky Park

How dark is the sky at Mayo Dark Sky Park?: Modelled zenith brightness from the 2024 World Atlas of Artificial Night Sky Brightness puts Mayo Dark Sky Park at about 21.87 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 Mayo Dark Sky Park from Belfast?: About 260.5 km in a straight line, heading west from Belfast. Using a 1.3 road-detour factor and staged average speeds that is roughly 338.7 km and 4 h of driving — an estimate, not a routed drive time.
When is the next moon-free dark window at Mayo Dark Sky Park?: The next stretch of essentially moon-free dark hours runs Nov 3–15 (13 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 Mayo Dark Sky Park?: Over 2021–2025, April (33%), May (31%), June (20%) had the highest share of nights with astronomical darkness that stayed clear (weighted cloud cover ≤ 20%); across the year it was 16%. 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.